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HAMDAN v. RUMSFELD (No. 05-184)
415 F. 3d 33, reversed and remanded.
Syllabus

Opinion
[Stevens]
Concurrence
[Breyer]
Concurrence
[Kennedy]
Dissent
[Scalia]
Dissent
[Thomas]
Dissent
[Alito]
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Justice Stevens, Opinion of the Court

NOTICE: This opinion is subject to formal revision before publication in the preliminary print of the United States Reports. Readers are requested to notify the Reporter of Decisions, Supreme Court of the United States, Washington, D. C. 20543, of any typographical or other formal errors, in order that corrections may be made before the preliminary print goes to press.

SUPREME COURT OF THE UNITED STATES

SALIM AHMED HAMDAN, PETITIONER v. DONALD
H. RUMSFELD, SECRETARY OF DEFENSE, et al.

on writ of certiorari to the united states court of appeals for the district of columbia circuit


[June 29, 2006]

    Justice Stevens announced the judgment of the Court and delivered the opinion of the Court with respect to Parts I through IV, Parts VI through VI–D–iii, Part VI–D–v, and Part VII, and an opinion with respect to Parts V and VI–D–iv, in which Justice Souter, Justice Ginsburg, and Justice Breyer join.

    Petitioner Salim Ahmed Hamdan, a Yemeni national, is in custody at an American prison in Guantanamo Bay, Cuba. In November 2001, during hostilities between the United States and the Taliban (which then governed Afghanistan), Hamdan was captured by militia forces and turned over to the U. S. military. In June 2002, he was transported to Guantanamo Bay. Over a year later, the President deemed him eligible for trial by military commission for then-unspecified crimes. After another year had passed, Hamdan was charged with one count of conspiracy “to commit … offenses triable by military commission.” App. to Pet. for Cert. 65a.

    Hamdan filed petitions for writs of habeas corpus and mandamus to challenge the Executive Branch’s intended means of prosecuting this charge. He concedes that a court-martial constituted in accordance with the Uniform Code of Military Justice (UCMJ), 10 U. S. C. §801 et seq. (2000 ed. and Supp. III), would have authority to try him. His objection is that the military commission the President has convened lacks such authority, for two principal reasons: First, neither congressional Act nor the common law of war supports trial by this commission for the crime of conspiracy—an offense that, Hamdan says, is not a violation of the law of war. Second, Hamdan contends, the procedures that the President has adopted to try him violate the most basic tenets of military and international law, including the principle that a defendant must be permitted to see and hear the evidence against him.

    The District Court granted Hamdan’s request for a writ of habeas corpus. 344 F. Supp. 2d 152 (DC 2004). The Court of Appeals for the District of Columbia Circuit reversed. 415 F. 3d 33 (2005). Recognizing, as we did over a half-century ago, that trial by military commission is an extraordinary measure raising important questions about the balance of powers in our constitutional structure, Ex parte Quirin, 317 U. S. 1, 19 (1942) , we granted certiorari. 546 U. S. ___ (2005).

    For the reasons that follow, we conclude that the military commission convened to try Hamdan lacks power to proceed because its structure and procedures violate both the UCMJ and the Geneva Conventions. Four of us also conclude, see Part V, infra, that the offense with which Hamdan has been charged is not an “offens[e] that by … the law of war may be tried by military commissions.” 10 U. S. C. §821.

I

    On September 11, 2001, agents of the al Qaeda terrorist organization hijacked commercial airplanes and attacked the World Trade Center in New York City and the national headquarters of the Department of Defense in Arlington, Virginia. Americans will never forget the devastation wrought by these acts. Nearly 3,000 civilians were killed.

    Congress responded by adopting a Joint Resolution authorizing the President to “use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks … in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons.” Authorization for Use of Military Force (AUMF), 115 Stat. 224, note following 50 U. S. C. §1541 (2000 ed., Supp. III). Acting pursuant to the AUMF, and having determined that the Taliban regime had supported al Qaeda, the President ordered the Armed Forces of the United States to invade Afghanistan. In the ensuing hostilities, hundreds of individuals, Hamdan among them, were captured and eventually detained at Guantanamo Bay.

    On November 13, 2001, while the United States was still engaged in active combat with the Taliban, the President issued a comprehensive military order intended to govern the “Detention, Treatment, and Trial of Certain Non-Citizens in the War Against Terrorism,” 66 Fed. Reg. 57833 (hereinafter November 13 Order or Order). Those subject to the November 13 Order include any noncitizen for whom the President determines “there is reason to believe” that he or she (1) “is or was” a member of al Qaeda or (2) has engaged or participated in terrorist activities aimed at or harmful to the United States. Id., at 57834. Any such individual “shall, when tried, be tried by military commission for any and all offenses triable by military commission that such individual is alleged to have committed, and may be punished in accordance with the penalties provided under applicable law, including imprisonment or death.” Ibid. The November 13 Order vested in the Secretary of Defense the power to appoint military commissions to try individuals subject to the Order, but that power has since been delegated to John D. Altenberg, Jr., a retired Army major general and longtime military lawyer who has been designated “Appointing Authority for Military Commissions.”

    On July 3, 2003, the President announced his determination that Hamdan and five other detainees at Guantanamo Bay were subject to the November 13 Order and thus triable by military commission. In December 2003, military counsel was appointed to represent Hamdan. Two months later, counsel filed demands for charges and for a speedy trial pursuant to Article 10 of the UCMJ, 10 U. S. C. §810. On February 23, 2004, the legal adviser to the Appointing Authority denied the applications, ruling that Hamdan was not entitled to any of the protections of the UCMJ. Not until July 13, 2004, after Hamdan had commenced this action in the United States District Court for the Western District of Washington, did the Government finally charge him with the offense for which, a year earlier, he had been deemed eligible for trial by military commission.

    The charging document, which is unsigned, contains 13 numbered paragraphs. The first two paragraphs recite the asserted bases for the military commission’s jurisdiction—namely, the November 13 Order and the President’s July 3, 2003, declaration that Hamdan is eligible for trial by military commission. The next nine paragraphs, collectively entitled “General Allegations,” describe al Qaeda’s activities from its inception in 1989 through 2001 and identify Osama bin Laden as the group’s leader. Hamdan is not mentioned in these paragraphs.

    Only the final two paragraphs, entitled “Charge: Conspiracy,” contain allegations against Hamdan. Paragraph 12 charges that “from on or about February 1996 to on or about November 24, 2001,” Hamdan “willfully and knowingly joined an enterprise of persons who shared a common criminal purpose and conspired and agreed with [named members of al Qaeda] to commit the following offenses triable by military commission: attacking civilians; attacking civilian objects; murder by an unprivileged belligerent; and terrorism.” App. to Pet. for Cert. 65a. There is no allegation that Hamdan had any command responsibilities, played a leadership role, or participated in the planning of any activity.

    Paragraph 13 lists four “overt acts” that Hamdan is alleged to have committed sometime between 1996 and November 2001 in furtherance of the “enterprise and conspiracy”: (1) he acted as Osama bin Laden’s “bodyguard and personal driver,” “believ[ing]” all the while that bin Laden “and his associates were involved in” terrorist acts prior to and including the attacks of September 11, 2001; (2) he arranged for transportation of, and actually transported, weapons used by al Qaeda members and by bin Laden’s bodyguards (Hamdan among them); (3) he “drove or accompanied [O]sama bin Laden to various al Qaida-sponsored training camps, press conferences, or lectures,” at which bin Laden encouraged attacks against Americans; and (4) he received weapons training at al Qaeda-sponsored camps. Id., at 65a–67a.

    After this formal charge was filed, the United States District Court for the Western District of Washington transferred Hamdan’s habeas and mandamus petitions to the United States District Court for the District of Columbia. Meanwhile, a Combatant Status Review Tribunal (CSRT) convened pursuant to a military order issued on July 7, 2004, decided that Hamdan’s continued detention at Guantanamo Bay was warranted because he was an “enemy combatant.”1 Separately, proceedings before the military commission commenced.

    On November 8, 2004, however, the District Court granted Hamdan’s petition for habeas corpus and stayed the commission’s proceedings. It concluded that the President’s authority to establish military commissions extends only to “offenders or offenses triable by military [commission] under the law of war,” 344 F. Supp. 2d, at 158; that the law of war includes the Geneva Convention (III) Relative to the Treatment of Prisoners of War, Aug. 12, 1949, [1955] 6 U. S. T. 3316, T. I. A. S. No. 3364 (Third Geneva Convention); that Hamdan is entitled to the full protections of the Third Geneva Convention until adjudged, in compliance with that treaty, not to be a prisoner of war; and that, whether or not Hamdan is properly classified as a prisoner of war, the military commission convened to try him was established in violation of both the UCMJ and Common Article 3 of the Third Geneva Convention because it had the power to convict based on evidence the accused would never see or hear. 344 F. Supp. 2d, at 158–172.

    The Court of Appeals for the District of Columbia Circuit reversed. Like the District Court, the Court of Appeals declined the Government’s invitation to abstain from considering Hamdan’s challenge. Cf. Schlesinger v. Councilman, 420 U. S. 738 (1975) . On the merits, the panel rejected the District Court’s further conclusion that Hamdan was entitled to relief under the Third Geneva Convention. All three judges agreed that the Geneva Conventions were not “judicially enforceable,” 415 F. 3d, at 38, and two thought that the Conventions did not in any event apply to Hamdan, id., at 40–42; but see id., at 44 (Williams, J., concurring). In other portions of its opinion, the court concluded that our decision in Quirin foreclosed any separation-of-powers objection to the military commission’s jurisdiction, and held that Hamdan’s trial before the contemplated commission would violate neither the UCMJ nor U. S. Armed Forces regulations intended to implement the Geneva Conventions. 415 F. 3d, at 38, 42–43.

    On November 7, 2005, we granted certiorari to decide whether the military commission convened to try Hamdan has authority to do so, and whether Hamdan may rely on the Geneva Conventions in these proceedings.

II

    On February 13, 2006, the Government filed a motion to dismiss the writ of certiorari. The ground cited for dismissal was the recently enacted Detainee Treatment Act of 2005 (DTA), Pub. L. 109–148, 119 Stat. 2739. We postponed our ruling on that motion pending argument on the merits, 546 U. S. ___ (2006), and now deny it.

    The DTA, which was signed into law on December 30, 2005, addresses a broad swath of subjects related to detainees. It places restrictions on the treatment and interrogation of detainees in U. S. custody, and it furnishes procedural protections for U. S. personnel accused of engaging in improper interrogation. DTA §§1002–1004, 119 Stat. 2739–2740. It also sets forth certain “procedures for status review of detainees outside the United States.” §1005, id., at 2740. Subsections (a) through (d) of §1005 direct the Secretary of Defense to report to Congress the procedures being used by CSRTs to determine the proper classification of detainees held in Guantanamo Bay, Iraq, and Afghanistan, and to adopt certain safeguards as part of those procedures.

    Subsection (e) of §1005, which is entitled “Judicial Review of Detention of Enemy Combatants,” supplies the basis for the Government’s jurisdictional argument. The subsection contains three numbered paragraphs. The first paragraph amends the judicial code as follows:

    “(1) In general.—Section 2241 of title 28, United States Code, is amended by adding at the end the following:

.     .     .     .     .

    “ ‘(e) Except as provided in section 1005 of the Detainee Treatment Act of 2005, no court, justice, or judge shall have jurisdiction to hear or consider—

    “ ‘(1) an application for a writ of habeas corpus filed by or on behalf of an alien detained by the Department of Defense at Guantanamo Bay, Cuba; or

    “ ‘(2) any other action against the United States or its agents relating to any aspect of the detention by the Department of Defense of an alien at Guantanamo Bay, Cuba, who—

    “ ‘(A) is currently in military custody; or

    “ ‘(B) has been determined by the United States Court of Appeals for the District of Columbia Circuit in accordance with the procedures set forth in section 1005(e) of the Detainee Treatment Act of 2005 to have been properly detained as an enemy combatant.’ ” §1005(e), id., at 2741–2742.

    Paragraph (2) of subsection (e) vests in the Court of Appeals for the District of Columbia Circuit the “exclusive jurisdiction to determine the validity of any final decision of a [CSRT] that an alien is properly designated as an enemy combatant.” Paragraph (2) also delimits the scope of that review. See §§1005(e)(2)(C)(i)–(ii), id., at 2742.

    Paragraph (3) mirrors paragraph (2) in structure, but governs judicial review of final decisions of military commissions, not CSRTs. It vests in the Court of Appeals for the District of Columbia Circuit “exclusive jurisdiction to determine the validity of any final decision rendered pursuant to Military Commission Order No. 1, dated August 31, 2005 (or any successor military order).” §1005(e)(3)(A), id., at 2743.2 Review is as of right for any alien sentenced to death or a term of imprisonment of 10 years or more, but is at the Court of Appeals’ discretion in all other cases. The scope of review is limited to the following inquiries:

    “(i) whether the final decision [of the military commission] was consistent with the standards and procedures specified in the military order referred to in subparagraph (A); and

    “(ii) to the extent the Constitution and laws of the United States are applicable, whether the use of such standards and procedures to reach the final decision is consistent with the Constitution and laws of the United States.” §1005(e)(3)(D), ibid.

    Finally, §1005 contains an “effective date” provision, which reads as follows:

    “(1) In general.—This section shall take effect on the date of the enactment of this Act.

    “(2) Review of Combatant Status Tribunal and Military Commission Decisions.—Paragraphs (2) and (3) of subsection (e) shall apply with respect to any claim whose review is governed by one of such paragraphs and that is pending on or after the date of the enactment of this Act.” §1005(h), id., at 2743–2744.3

The Act is silent about whether paragraph (1) of subsection (e) “shall apply” to claims pending on the date of enactment.

    The Government argues that §§1005(e)(1) and 1005(h) had the immediate effect, upon enactment, of repealing federal jurisdiction not just over detainee habeas actions yet to be filed but also over any such actions then pending in any federal court—including this Court. Accordingly, it argues, we lack jurisdiction to review the Court of Appeals’ decision below.

    Hamdan objects to this theory on both constitutional and statutory grounds. Principal among his constitutional arguments is that the Government’s preferred reading raises grave questions about Congress’ authority to impinge upon this Court’s appellate jurisdiction, particularly in habeas cases. Support for this argument is drawn from Ex parte Yerger, 8Wall. 85 (1869), in which, having explained that “the denial to this court of appellate jurisdiction” to consider an original writ of habeas corpus would “greatly weaken the efficacy of the writ,” id., at 102–103, we held that Congress would not be presumed to have effected such denial absent an unmistakably clear statement to the contrary. See id., at 104–105; see also Felker v. Turpin, 518 U. S. 651 (1996) ; Durousseau v. United States, 6 Cranch 307, 314 (1810) (opinion for the Court by Marshall, C. J.) (The “appellate powers of this court” are not created by statute but are “given by the constitution”); United States v. Klein, 13Wall. 128 (1872). Cf. Ex parte McCardle, 7Wall. 506, 514 (1869) (holding that Congress had validly foreclosed one avenue of appellate review where its repeal of habeas jurisdiction, reproduced in the margin,4 could not have been “a plainer instance of positive exception”). Hamdan also suggests that, if the Government’s reading is correct, Congress has unconstitutionally suspended the writ of habeas corpus.

    We find it unnecessary to reach either of these arguments. Ordinary principles of statutory construction suffice to rebut the Government’s theory—at least insofar as this case, which was pending at the time the DTA was enacted, is concerned.

    The Government acknowledges that only paragraphs (2) and (3) of subsection (e) are expressly made applicable to pending cases, see §1005(h)(2), 119 Stat. 2743–2744, but argues that the omission of paragraph (1) from the scope of that express statement is of no moment. This is so, we are told, because Congress’ failure to expressly reserve federal courts’ jurisdiction over pending cases erects a presumption against jurisdiction, and that presumption is rebutted by neither the text nor the legislative history of the DTA.

    The first part of this argument is not entirely without support in our precedents. We have in the past “applied intervening statutes conferring or ousting jurisdiction, whether or not jurisdiction lay when the underlying conduct occurred or when the suit was filed.” Landgraf v. USI Film Products, 511 U. S. 244, 274 (1994) (citing Bruner v. United States, 343 U. S. 112 (1952) ; Hallowell v. Commons, 239 U. S. 506 (1916) ); see Republic of Austria v. Altmann, 541 U. S. 677, 693 (2004) . But the “presumption” that these cases have applied is more accurately viewed as the nonapplication of another presumption—viz., the presumption against retroactivity—in certain limited circumstances.5 If a statutory provision “would operate retroactively” as applied to cases pending at the time the provision was enacted, then “our traditional presumption teaches that it does not govern absent clear congressional intent favoring such a result.” Landgraf, 511 U. S., at 280. We have explained, however, that, unlike other intervening changes in the law, a jurisdiction-conferring or jurisdiction-stripping statute usually “takes away no substantive right but simply changes the tribunal that is to hear the case.” Hallowell, 239 U. S., at 508. If that is truly all the statute does, no retroactivity problem arises because the change in the law does not “impair rights a party possessed when he acted, increase a party’s liability for past conduct, or impose new duties with respect to transactions already completed.” Landgraf, 511 U. S., at 280.6 And if a new rule has no retroactive effect, the presumption against retroactivity will not prevent its application to a case that was already pending when the new rule was enacted.

    That does not mean, however, that all jurisdiction-stripping provisions—or even all such provisions that truly lack retroactive effect—must apply to cases pending at the time of their enactment.7 “[N]ormal rules of construction,” including a contextual reading of the statutory language, may dictate otherwise. Lindh v. Murphy, 521 U. S. 320, 326 (1997) .8 A familiar principle of statutory construction, relevant both in Lindh and here, is that a negative inference may be drawn from the exclusion of language from one statutory provision that is included in other provisions of the same statute. See id., at 330; see also, e.g., Russello v. United States, 464 U. S. 16, 23 (1983) (“ ‘[W]here Congress includes particular language in one section of a statute but omits it in another section of the same Act, it is generally presumed that Congress acts intentionally and purposely in the disparate inclusion or exclusion’ ”). The Court in Lindh relied on this reasoning to conclude that certain limitations on the availability of habeas relief imposed by AEDPA applied only to cases filed after that statute’s effective date. Congress’ failure to identify the temporal reach of those limitations, which governed noncapital cases, stood in contrast to its express command in the same legislation that new rules governing habeas petitions in capital cases “apply to cases pending on or after the date of enactment.” §107(c), 110 Stat. 1226; see Lindh, 521 U. S., at 329–330. That contrast, combined with the fact that the amendments at issue “affect[ed] substantive entitlement to relief,” id., at 327, warranted drawing a negative inference.

    A like inference follows a fortiori from Lindh in this case. “If … Congress was reasonably concerned to ensure that [§§1005(e)(2) and (3)] be applied to pending cases, it should have been just as concerned about [§1005(e)(1)], unless it had the different intent that the latter [section] not be applied to the general run of pending cases.” Id., at 329. If anything, the evidence of deliberate omission is stronger here than it was in Lindh. In Lindh, the provisions to be contrasted had been drafted separately but were later “joined together and … considered simultaneously when the language raising the implication was inserted.” Id., at 330. We observed that Congress’ tandem review and approval of the two sets of provisions strengthened the presumption that the relevant omission was deliberate. Id., at 331; see also Field v. Mans, 516 U. S. 59, 75 (1995) (“The more apparently deliberate the contrast, the stronger the inference, as applied, for example, to contrasting statutory sections originally enacted simultaneously in relevant respects”). Here, Congress not only considered the respective temporal reaches of paragraphs (1), (2), and (3) of subsection (e) together at every stage, but omitted paragraph (1) from its directive that paragraphs (2) and (3) apply to pending cases only after having rejected earlier proposed versions of the statute that would have included what is now paragraph (1) within the scope of that directive. Compare DTA §1005(h)(2), 119 Stat. 2743–2744, with 151 Cong. Rec. S12655 (Nov. 10, 2005) (S. Amdt. 2515); see id., at S14257–S14258 (Dec. 21, 2005) (discussing similar language proposed in both the House and the Senate).9 Congress’ rejection of the very language that would have achieved the result the Government urges here weighs heavily against the Government’s interpretation. See Doe v. Chao, 540 U. S. 614, 621–623 (2004) .10

    The Government nonetheless offers two reasons why, in its view, no negative inference may be drawn in favor of jurisdiction. First, it asserts that Lindh is inapposite because “Section 1005(e)(1) and (h)(1) remove jurisdiction, while Section 1005(e)(2), (3) and (h)(2) create an exclusive review mechanism and define the nature of that review.” Reply Brief in Support of Respondents’ Motion to Dismiss 4. Because the provisions being contrasted “address wholly distinct subject matters,” Martin v. Hadix, 527 U. S. 343, 356 (1999) , the Government argues, Congress’ different treatment of them is of no significance.

    This argument must fail because it rests on a false distinction between the “jurisdictional” nature of subsection (e)(1) and the “procedural” character of subsections (e)(2) and (e)(3). In truth, all three provisions govern jurisdiction over detainees’ claims; subsection (e)(1) addresses jurisdiction in habeas cases and other actions “relating to any aspect of the detention,” while subsections (e)(2) and (3) vest exclusive,11 but limited, jurisdiction in the Court of Appeals for the District of Columbia Circuit to review “final decision[s]” of CSRTs and military commissions.

    That subsection (e)(1) strips jurisdiction while subsections (e)(2) and (e)(3) restore it in limited form is hardly a distinction upon which a negative inference must founder. Justice Scalia, in arguing to the contrary, maintains that Congress had “ample reason” to provide explicitly for application of subsections (e)(2) and (e)(3) to pending cases because “jurisdiction-stripping” provisions like subsection (e)(1) have been treated differently under our retroactivity jurisprudence than “jurisdiction-conferring” ones like subsections (e)(2) and (e)(3). Post, at 8 (dissenting opinion); see also Reply Brief in Support of Respondents’ Motion to Dismiss 5–6. That theory is insupportable. Assuming arguendo that subsections (e)(2) and (e)(3) “confer new jurisdiction (in the D. C. Circuit) where there was none before,” post, at 8 (emphasis in original); but see Rasul v. Bush, 542 U. S. 466 (2004) , and that our precedents can be read to “strongly indicat[e]” that jurisdiction-creating statutes raise special retroactivity concerns not also raised by jurisdiction-stripping statutes, post, at 8,12 subsections (e)(2) and (e)(3) “confer” jurisdiction in a manner that cannot conceivably give rise to retroactivity questions under our precedents. The provisions impose no additional liability or obligation on any private party or even on the United States, unless one counts the burden of litigating an appeal—a burden not a single one of our cases suggests triggers retroactivity concerns.13 Moreover, it strains credulity to suggest that the desire to reinforce the application of subsections (e)(2) and (e)(3) to pending cases drove Congress to exclude subsection (e)(1) from §1005(h)(2).

    The Government’s second objection is that applying subsections (e)(2) and (e)(3) but not (e)(1) to pending cases “produces an absurd result” because it grants (albeit only temporarily) dual jurisdiction over detainees’ cases in circumstances where the statute plainly envisions that the District of Columbia Circuit will have “exclusive” and immediate jurisdiction over such cases. Reply Brief in Support of Respondents’ Motion to Dismiss 7. But the premise here is faulty; subsections (e)(2) and (e)(3) grant jurisdiction only over actions to “determine the validity of any final decision” of a CSRT or commission. Because Hamdan, at least, is not contesting any “final decision” of a CSRT or military commission, his action does not fall within the scope of subsection (e)(2) or (e)(3). There is, then, no absurdity.14

    The Government’s more general suggestion that Congress can have had no good reason for preserving habeas jurisdiction over cases that had been brought by detainees prior to enactment of the DTA not only is belied by the legislative history, see n. 10, supra, but is otherwise without merit. There is nothing absurd about a scheme under which pending habeas actions—particularly those, like this one, that challenge the very legitimacy of the tribunals whose judgments Congress would like to have reviewed—are preserved, and more routine challenges to final decisions rendered by those tribunals are carefully channeled to a particular court and through a particular lens of review.

    Finally, we cannot leave unaddressed Justice Scalia’s contentions that the “meaning of §1005(e)(1) is entirely clear,” post, at 6, and that “the plain import of a statute repealing jurisdiction is to eliminate the power to consider and render judgment—in an already pending case no less than in a case yet to be filed,” post, at 3 (emphasis in original). Only by treating the Bruner rule as an inflexible trump (a thing it has never been, see n. 7, supra) and ignoring both the rest of §1005’s text and its drafting history can one conclude as much. Congress here expressly provided that subsections (e)(2) and (e)(3) applied to pending cases. It chose not to so provide—after having been presented with the option—for subsection (e)(1). The omission is an integral part of the statutory scheme that muddies whatever “plain meaning” may be discerned from blinkered study of subsection (e)(1) alone. The dissent’s speculation about what Congress might have intended by the omission not only is counterfactual, cf. n. 10, supra (recounting legislative history), but rests on both a misconstruction of the DTA and an erroneous view our precedents, see supra, at 17, and n. 12.

    For these reasons, we deny the Government’s motion to dismiss.15

III

    Relying on our decision in Councilman, 420 U. S. 738 , the Government argues that, even if we have statutory jurisdiction, we should apply the “judge-made rule that civilian courts should await the final outcome of on-going military proceedings before entertaining an attack on those proceedings.” Brief for Respondents 12. Like the District Court and the Court of Appeals before us, we reject this argument.

    In Councilman, an army officer on active duty was referred to a court-martial for trial on charges that he violated the UCMJ by selling, transferring, and possessing marijuana. 420 U. S., at 739–740. Objecting that the alleged offenses were not “ ‘service connected,’ ” id., at 740, the officer filed suit in Federal District Court to enjoin the proceedings. He neither questioned the lawfulness of courts-martial or their procedures nor disputed that, as a serviceman, he was subject to court-martial jurisdiction. His sole argument was that the subject matter of his case did not fall within the scope of court-martial authority. See id., at 741, 759. The District Court granted his request for injunctive relief, and the Court of Appeals affirmed.

    We granted certiorari and reversed. Id., at 761. We did not reach the merits of whether the marijuana charges were sufficiently “service connected” to place them within the subject-matter jurisdiction of a court-martial. Instead, we concluded that, as a matter of comity, federal courts should normally abstain from intervening in pending court-martial proceedings against members of the Armed Forces,16 and further that there was nothing in the particular circumstances of the officer’s case to displace that general rule. See id., at 740, 758.

    Councilman identifies two considerations of comity that together favor abstention pending completion of ongoing court-martial proceedings against service personnel. See New v. Cohen, 129 F. 3d 639, 643 (CADC 1997); see also 415 F. 3d, at 36–37 (discussing Councilman and New). First, military discipline and, therefore, the efficient operation of the Armed Forces are best served if the military justice system acts without regular interference from civilian courts. See Councilman, 420 U. S., at 752. Second, federal courts should respect the balance that Congress struck between military preparedness and fairness to individual service members when it created “an integrated system of military courts and review procedures, a critical element of which is the Court of Military Appeals, consisting of civilian judges ‘completely removed from all military influence or persuasion … .’ ” Id., at 758 (quoting H. R. Rep. No. 491, 81st Cong., 1st Sess., p. 7 (1949)). Just as abstention in the face of ongoing state criminal proceedings is justified by our expectation that state courts will enforce federal rights, so abstention in the face of ongoing court-martial proceedings is justified by our expectation that the military court system established by Congress—with its substantial procedural protections and provision for appellate review by independent civilian judges—“will vindicate servicemen’s constitutional rights,” 420 U. S., at 758. See id., at 755–758.17

    The same cannot be said here; indeed, neither of the comity considerations identified in Councilman weighs in favor of abstention in this case. First, Hamdan is not a member of our Nation’s Armed Forces, so concerns about military discipline do not apply. Second, the tribunal convened to try Hamdan is not part of the integrated system of military courts, complete with independent review panels, that Congress has established. Unlike the officer in Councilman,Hamdan has no right to appeal any conviction to the civilian judges of the Court of Military Appeals (now called the United States Court of Appeals for the Armed Forces, see Pub. L. 103–337, 108 Stat. 2831). Instead, under Dept. of Defense Military Commission Order No. 1 (Commission Order No. 1), which was issued by the President on March 21, 2002, and amended most recently on August 31, 2005, and which governs the procedures for Hamdan’s commission, any conviction would be reviewed by a panel consisting of three military officers designated by the Secretary of Defense. Commission Order No. 1 §6(H)(4). Commission Order No. 1 provides that appeal of a review panel’s decision may be had only to the Secretary of Defense himself, §6(H)(5), and then, finally, to the President, §6(H)(6).18

    We have no doubt that the various individuals assigned review power under Commission Order No. 1 would strive to act impartially and ensure that Hamdan receive all protections to which he is entitled. Nonetheless, these review bodies clearly lack the structural insulation from military influence that characterizes the Court of Appeals for the Armed Forces, and thus bear insufficient conceptual similarity to state courts to warrant invocation of abstention principles.19

    In sum, neither of the two comity considerations underlying our decision to abstain in Councilman applies to the circumstances of this case. Instead, this Court’s decision in Quirin is the most relevant precedent. In Quirin, seven German saboteurs were captured upon arrival by submarine in New York and Florida. 317 U. S., at 21. The President convened a military commission to try the saboteurs, who then filed habeas corpus petitions in the United States District Court for the District of Columbia challenging their trial by commission. We granted the saboteurs’ petition for certiorari to the Court of Appeals before judgment. See id., at 19. Far from abstaining pending the conclusion of military proceedings, which were ongoing, we convened a special Term to hear the case and expedited our review. That course of action was warranted, we explained, “[i]n view of the public importance of the questions raised by [the cases] and of the duty which rests on the courts, in time of war as well as in time of peace, to preserve unimpaired the constitutional safeguards of civil liberty, and because in our opinion the public interest required that we consider and decide those questions without any avoidable delay.” Ibid.

    As the Court of Appeals here recognized, Quirin “provides a compelling historical precedent for the power of civilian courts to entertain challenges that seek to interrupt the processes of military commissions.” 415 F. 3d, at 36.20 The circumstances of this case, like those in Quirin, simply do not implicate the “obligations of comity” that, under appropriate circumstances, justify abstention. Quackenbush v. Allstate Ins. Co., 517 U. S. 706, 733 (1996) (Kennedy, J., concurring).

    Finally, the Government has identified no other “important countervailing interest” that would permit federal courts to depart from their general “duty to exercise the jurisdiction that is conferred upon them by Congress.” Id., at 716 (majority opinion). To the contrary, Hamdan and the Government both have a compelling interest in knowing in advance whether Hamdan may be tried by a military commission that arguably is without any basis in law and operates free from many of the procedural rules prescribed by Congress for courts-martial—rules intended to safeguard the accused and ensure the reliability of any conviction. While we certainly do not foreclose the possibility that abstention may be appropriate in some cases seeking review of ongoing military commission proceedings (such as military commissions convened on the battlefield), the foregoing discussion makes clear that, under our precedent, abstention is not justified here. We therefore proceed to consider the merits of Hamdan’s challenge.

IV

    The military commission, a tribunal neither mentioned in the Constitution nor created by statute, was born of military necessity. See W. Winthrop, Military Law and Precedents 831 (rev. 2d ed. 1920) (hereinafter Winthrop). Though foreshadowed in some respects by earlier tribunals like the Board of General Officers that General Washington convened to try British Major John André for spying during the Revolutionary War, the commission “as such” was inaugurated in 1847. Id., at 832; G. Davis, A Treatise on the Military Law of the United States 308 (2d ed. 1909) (hereinafter Davis). As commander of occupied Mexican territory, and having available to him no other tribunal, General Winfield Scott that year ordered the establishment of both “ ‘military commissions’ ” to try ordinary crimes committed in the occupied territory and a “council of war” to try offenses against the law of war. Winthrop 832 (emphases in original).

    When the exigencies of war next gave rise to a need for use of military commissions, during the Civil War, the dual system favored by General Scott was not adopted. Instead, a single tribunal often took jurisdiction over ordinary crimes, war crimes, and breaches of military orders alike. As further discussed below, each aspect of that seemingly broad jurisdiction was in fact supported by a separate military exigency. Generally, though, the need for military commissions during this period—as during the Mexican War—was driven largely by the then very limited jurisdiction of courts-martial: “The occasion for the military commission arises principally from the fact that the jurisdiction of the court-martial proper, in our law, is restricted by statute almost exclusively to members of the military force and to certain specific offences defined in a written code.” Id., at 831 (emphasis in original).

    Exigency alone, of course, will not justify the establishment and use of penal tribunals not contemplated by Article I, §8 and Article III, §1 of the Constitution unless some other part of that document authorizes a response to the felt need. See Ex parte Milligan, 4Wall. 2, 121 (1866) (“Certainly no part of the judicial power of the country was conferred on [military commissions]”); Ex parte Vallandigham, 1Wall. 243, 251 (1864); see also Quirin, 317 U. S., at 25 (“Congress and the President, like the courts, possess no power not derived from the Constitution”). And that authority, if it exists, can derive only from the powers granted jointly to the President and Congress in time of war. See id., at 26–29; In re Yamashita, 327 U. S. 1, 11 (1946) .

    The Constitution makes the President the “Commander in Chief” of the Armed Forces, Art. II, §2, cl. 1, but vests in Congress the powers to “declare War … and make Rules concerning Captures on Land and Water,” Art. I, §8, cl. 11, to “raise and support Armies,” id., cl. 12, to “define and punish … Offences against the Law of Nations,” id., cl. 10, and “To make Rules for the Government and Regulation of the land and naval Forces,” id., cl. 14. The interplay between these powers was described by Chief Justice Chase in the seminal case of Ex parte Milligan:

“The power to make the necessary laws is in Congress; the power to execute in the President. Both powers imply many subordinate and auxiliary powers. Each includes all authorities essential to its due exercise. But neither can the President, in war more than in peace, intrude upon the proper authority of Congress, nor Congress upon the proper authority of the President… . Congress cannot direct the conduct of campaigns, nor can the President, or any commander under him, without the sanction of Congress, institute tribunals for the trial and punishment of offences, either of soldiers or civilians, unless in cases of a controlling necessity, which justifies what it compels, or at least insures acts of indemnity from the justice of the legislature.” 4 Wall., at 139–140.21

    Whether Chief Justice Chase was correct in suggesting that the President may constitutionally convene military commissions “without the sanction of Congress” in cases of “controlling necessity” is a question this Court has not answered definitively, and need not answer today. For we held in Quirin that Congress had, through Article of War 15, sanctioned the use of military commissions in such circumstances. 317 U. S., at 28 (“By the Articles of War, and especially Article 15, Congress has explicitly provided, so far as it may constitutionally do so, that military tribunals shall have jurisdiction to try offenders or offenses against the law of war in appropriate cases”). Article 21 of the UCMJ, the language of which is substantially identical to the old Article 15 and was preserved by Congress after World War II,22 reads as follows:

“Jurisdiction of courts-martial not exclusive.

“The provisions of this code conferring jurisdiction upon courts-martial shall not be construed as depriving military commissions, provost courts, or other military tribunals of concurrent jurisdiction in respect of offenders or offenses that by statute or by the law of war may be tried by such military commissions, provost courts, or other military tribunals.” 64 Stat. 115.

    We have no occasion to revisit Quirin’s controversial characterization of Article of War 15 as congressional authorization for military commissions. Cf. Brief for Legal Scholars and Historians as Amici Curiae 12–15. Contrary to the Government’s assertion, however, even Quirin did not view the authorization as a sweeping mandate for the President to “invoke military commissions when he deems them necessary.” Brief for Respondents 17. Rather, the Quirin Court recognized that Congress had simply preserved what power, under the Constitution and the common law of war, the President had had before 1916 to convene military commissions—with the express condition that the President and those under his command comply with the law of war. See 317 U. S., at 28–29.23 That much is evidenced by the Court’s inquiry, following its conclusion that Congress had authorized military commissions, into whether the law of war had indeed been complied with in that case. See ibid.

The Government would have us dispense with the inquiry that the Quirin Court undertook and find in either the AUMF or the DTA specific, overriding authorization for the very commission that has been convened to try Hamdan. Neither of these congressional Acts, however, expands the President’s authority to convene military commissions. First, while we assume that the AUMF activated the President’s war powers, see Hamdi v. Rumsfeld, 542 U. S. 507 (2004) (plurality opinion), and that those powers include the authority to convene military commissions in appropriate circumstances, see id., at 518; Quirin, 317 U. S., at 28–29; see also Yamashita, 327 U. S., at 11, there is nothing in the text or legislative history of the AUMF even hinting that Congress intended to expand or alter the authorization set forth in Article 21 of the UCMJ. Cf. Yerger, 8 Wall., at 105 (“Repeals by implication are not favored”).24

    Likewise, the DTA cannot be read to authorize this commission. Although the DTA, unlike either Article 21 or the AUMF, was enacted after the President had convened Hamdan’s commission, it contains no language authorizing that tribunal or any other at Guantanamo Bay. The DTA obviously “recognize[s]” the existence of the Guantanamo Bay commissions in the weakest sense, Brief for Respondents 15, because it references some of the military orders governing them and creates limited judicial review of their “final decision[s],” DTA §1005(e)(3), 119 Stat. 2743. But the statute also pointedly reserves judgment on whether “the Constitution and laws of the United States are applicable” in reviewing such decisions and whether, if they are, the “standards and procedures” used to try Hamdan and other detainees actually violate the “Constitution and laws.” Ibid.

Together, the UCMJ, the AUMF, and the DTA at most acknowledge a general Presidential authority to convene military commissions in circumstances where justified under the “Constitution and laws,” including the law of war. Absent a more specific congressional authorization, the task of this Court is, as it was in Quirin, to decide whether Hamdan’s military commission is so justified. It is to that inquiry we now turn.

V

    The common law governing military commissions may be gleaned from past practice and what sparse legal precedent exists. Commissions historically have been used in three situations. See Bradley & Goldsmith, Congressional Authorization and the War on Terrorism, 118 Harv. L. Rev. 2048, 2132–2133 (2005); Winthrop 831–846; Hearings on H. R. 2498 before the Subcommittee of the House Committee on Armed Services, 81st Cong., 1st Sess., 975 (1949). First, they have substituted for civilian courts at times and in places where martial law has been declared. Their use in these circumstances has raised constitutional questions, see Duncan v. Kahanamoku, 327 U. S. 304 (1946) ; Milligan, 4 Wall., at 121–122, but is well recognized.25 See Winthrop 822, 836–839. Second, commissions have been established to try civilians “as part of a temporary military government over occupied enemy territory or territory regained from an enemy where civilian government cannot and does not function.” Duncan, 327 U. S., at 314; see Milligan, 4 Wall., at 141–142 (Chase, C. J., concurring in judgment) (distinguishing “martial law proper” from “military government” in occupied territory). Illustrative of this second kind of commission is the one that was established, with jurisdiction to apply the German Criminal Code, in occupied Germany following the end of World War II. See Madsen v. Kinsella, 343 U. S. 341, 356 (1952) .26

    The third type of commission, convened as an “incident to the conduct of war” when there is a need “to seize and subject to disciplinary measures those enemies who in their attempt to thwart or impede our military effort have violated the law of war,” Quirin, 317 U. S., at 28–29, has been described as “utterly different” from the other two. Bickers, Military Commissions are Constitutionally Sound: A Response to Professors Katyal and Tribe, 34 Tex. Tech. L. Rev. 899, 902 (2002–2003).27 Not only is its jurisdiction limited to offenses cognizable during time of war, but its role is primarily a factfinding one—to determine, typically on the battlefield itself, whether the defendant has violated the law of war. The last time the U. S. Armed Forces

used the law-of-war military commission was during World War II. In Quirin, this Court sanctioned President Roosevelt’s use of such a tribunal to try Nazi saboteurs captured on American soil during the War. 317 U. S. 1 . And in Yamashita, we held that a military commission had jurisdiction to try a Japanese commander for failing to prevent troops under his command from committing atrocities in the Philippines. 327 U. S. 1 .

    Quirin is the model the Government invokes most frequently to defend the commission convened to try Hamdan. That is both appropriate and unsurprising. Since Guantanamo Bay is neither enemy-occupied territory nor under martial law, the law-of-war commission is the only model available. At the same time, no more robust model of executive power exists; Quirin represents the high-water mark of military power to try enemy combatants for war crimes.

    The classic treatise penned by Colonel William Winthrop, whom we have called “the ‘Blackstone of Military Law,’ ” Reid v. Covert, 354 U. S. 1 , n. 38 (1957) (plurality opinion), describes at least four preconditions for exercise of jurisdiction by a tribunal of the type convened to try Hamdan. First, “[a] military commission, (except where otherwise authorized by statute), can legally assume jurisdiction only of offenses committed within the field of the command of the convening commander.” Winthrop 836. The “field of command” in these circumstances means the “theatre of war.” Ibid. Second, the offense charged “must have been committed within the period of the war.”28 Id., at 837. No jurisdiction exists to try offenses “committed either before or after the war.” Ibid. Third, a military commission not established pursuant to martial law or an occupation may try only “[i]ndividuals of the enemy’s army who have been guilty of illegitimate warfare or other offences in violation of the laws of war” and members of one’s own army “who, in time of war, become chargeable with crimes or offences not cognizable, or triable, by the criminal courts or under the Articles of war.” Id., at 838. Finally, a law-of-war commission has jurisdiction to try only two kinds of offense: “Violations of the laws and usages of war cognizable by military tribunals only,” and “[b]reaches of military orders or regulations for which offenders are not legally triable by court-martial under the Articles of war.” Id., at 839.29

    All parties agree that Colonel Winthrop’s treatise accurately describes the common law governing military commissions, and that the jurisdictional limitations he identifies were incorporated in Article of War 15 and, later, Article 21 of the UCMJ. It also is undisputed that Hamdan’s commission lacks jurisdiction to try him unless the charge “properly set[s] forth, not only the details of the act charged, but the circumstances conferring jurisdiction.” Id., at 842 (emphasis in original). The question is whether the preconditions designed to ensure that a military necessity exists to justify the use of this extraordinary tribunal have been satisfied here.

    The charge against Hamdan, described in detail in Part I, supra, alleges a conspiracy extending over a number of years, from 1996 to November 2001.30 All but two months of that more than 5-year-long period preceded the attacks of September 11, 2001, and the enactment of the AUMF—the Act of Congress on which the Government relies for exercise of its war powers and thus for its authority to convene military commissions.31 Neither the purported agreement with Osama bin Laden and others to commit war crimes, nor a single overt act, is alleged to have occurred in a theater of war or on any specified date after September 11, 2001. None of the overt acts that Hamdan is alleged to have committed violates the law of war.

    These facts alone cast doubt on the legality of the charge and, hence, the commission; as Winthrop makes plain, the offense alleged must have been committed both in a theater of war and during, not before, the relevant conflict. But the deficiencies in the time and place allegations also underscore—indeed are symptomatic of—the most serious defect of this charge: The offense it alleges is not triable by law-of-war military commission. See Yamashita, 327 U. S., at 13 (“Neither congressional action nor the military orders constituting the commission authorized it to place petitioner on trial unless the charge proffered against him is of a violation of the law of war”).32

    There is no suggestion that Congress has, in exercise of its constitutional authority to “define and punish . . . Offences against the Law of Nations,” U. S. Const., Art. I, §8, cl. 10, positively identified “conspiracy” as a war crime.33 As we explained in Quirin, that is not necessarily fatal to the Government’s claim of authority to try the alleged offense by military commission; Congress, through Article 21 of the UCMJ, has “incorporated by reference” the common law of war, which may render triable by military commission certain offenses not defined by statute. 317 U. S., at 30. When, however, neither the elements of the offense nor the range of permissible punishments is defined by statute or treaty, the precedent must be plain and unambiguous. To demand any less would be to risk concentrating in military hands a degree of adjudicative and punitive power in excess of that contemplated either by statute or by the Constitution. Cf. Loving v. United States, 517 U. S. 748, 771 (1996) (acknowledging that Congress “may not delegate the power to make laws”); Reid, 354 U. S., at 23–24 (“The Founders envisioned the army as a necessary institution, but one dangerous to liberty if not confined within its essential bounds”); The Federalist No. 47, p. 324 (J. Cooke ed. 1961) (J. Madison) (“The accumulation of all powers legislative, executive and judiciary in the same hands … may justly be pronounced the very definition of tyranny”).34

    This high standard was met in Quirin; the violation there alleged was, by “universal agreement and practice” both in this country and internationally, recognized as an offense against the law of war. 317 U. S., at 30; see id., at 35–36 (“This precept of the law of war has been so recognized in practice both here and abroad, and has so generally been accepted as valid by authorities on international law that we think it must be regarded as a rule or principle of the law of war recognized by this Government by its enactment of the Fifteenth Article of War” (footnote omitted)). Although the picture arguably was less clear in Yamashita, compare 327 U. S., at 16 (stating that the provisions of the Fourth Hague Convention of 1907, 36 Stat. 2306, “plainly” required the defendant to control the troops under his command), with 327 U. S., at 35 (Murphy, J., dissenting), the disagreement between the majority and the dissenters in that case concerned whether the historic and textual evidence constituted clear precedent—not whether clear precedent was required to justify trial by law-of-war military commission.

    At a minimum, the Government must make a substantial showing that the crime for which it seeks to try a defendant by military commission is acknowledged to be an offense against the law of war. That burden is far from satisfied here. The crime of “conspiracy” has rarely if ever been tried as such in this country by any law-of-war military commission not exercising some other form of jurisdiction,35 and does not appear in either the Geneva Conventions or the Hague Conventions—the major treaties on the law of war.36 Winthrop explains that under the common law governing military commissions, it is not enough to intend to violate the law of war and commit overt acts in furtherance of that intention unless the overt acts either are themselves offenses against the law of war or constitute steps sufficiently substantial to qualify as an attempt. See Winthrop 841 (“[T]he jurisdiction of the military commission should be restricted to cases of offence consisting in overt acts, i.e., in unlawful commissions or actual attempts to commit, and not in intentions merely” (emphasis in original)).

    The Government cites three sources that it says show otherwise. First, it points out that the Nazi saboteurs in Quirin were charged with conspiracy. See Brief for Respondents 27. Second, it observes that Winthrop at one point in his treatise identifies conspiracy as an offense “prosecuted by military commissions.” Ibid. (citing Winthrop 839, and n. 5). Finally, it notes that another military historian, Charles Roscoe Howland, lists conspiracy “ ‘to violate the laws of war by destroying life or property in aid of the enemy’ ” as an offense that was tried as a violation of the law of war during the Civil War. Brief for Respondents 27–28 (citing C. Howland, Digest of Opinions of the Judge Advocates General of the Army 1071 (1912) (hereinafter Howland)). On close analysis, however, these sources at best lend little support to the Government’s position and at worst undermine it. By any measure, they fail to satisfy the high standard of clarity required to justify the use of a military commission.

    That the defendants in Quirin were charged with conspiracy is not persuasive, since the Court declined to address whether the offense actually qualified as a violation of the law of war—let alone one triable by military commission. The Quirin defendants were charged with the following offenses:

“[I.] Violation of the law of war.

“[II.] Violation of Article 81 of the Articles of War, defining the offense of relieving or attempting to relieve, or corresponding with or giving intelligence to, the enemy.

“[III.] Violation of Article 82, defining the offense of spying.

“[IV.] Conspiracy to commit the offenses alleged in charges [I, II, and III].” 317 U. S., at 23.

The Government, defending its charge, argued that the conspiracy alleged “constitute[d] an additional violation of the law of war.” Id., at 15. The saboteurs disagreed; they maintained that “[t]he charge of conspiracy can not stand if the other charges fall.” Id., at 8. The Court, however, declined to resolve the dispute. It concluded, first, that the specification supporting Charge I adequately alleged a “violation of the law of war” that was not “merely colorable or without foundation.” Id., at 36. The facts the Court deemed sufficient for this purpose were that the defendants, admitted enemy combatants, entered upon U. S. territory in time of war without uniform “for the purpose of destroying property used or useful in prosecuting the war.” That act was “a hostile and warlike” one. Id., at 36, 37. The Court was careful in its decision to identify an overt, “complete” act. Responding to the argument that the saboteurs had “not actually committed or attempted to commit any act of depredation or entered the theatre or zone of active military operations” and therefore had not violated the law of war, the Court responded that they had actually “passed our military and naval lines and defenses or went behind those lines, in civilian dress and with hostile purpose.” Id., at 38. “The offense was complete when with that purpose they entered—or, having so entered, they remained upon—our territory in time of war without uniform or other appropriate means of identification.” Ibid.

Turning to the other charges alleged, the Court explained that “[s]ince the first specification of Charge I sets forth a violation of the law of war, we have no occasion to pass on the adequacy of the second specification of Charge I, or to construe the 81st and 82nd Articles of War for the purpose of ascertaining whether the specifications under Charges II and III allege violations of those Articles or whether if so construed they are constitutional.” Id., at 46. No mention was made at all of Charge IV—the conspiracy charge.

    If anything, Quirin supports Hamdan’s argument that conspiracy is not a violation of the law of war. Not only did the Court pointedly omit any discussion of the conspiracy charge, but its analysis of Charge I placed special emphasis on the completion of an offense; it took seriously the saboteurs’ argument that there can be no violation of a law of war—at least not one triable by military commission—without the actual commission of or attempt to commit a “hostile and warlike act.” Id., at 37–38.

    That limitation makes eminent sense when one considers the necessity from whence this kind of military commission grew: The need to dispense swift justice, often in the form of execution, to illegal belligerents captured on the battlefield. See S. Rep. No. 130, 64th Cong., 1st Sess., p. 40 (1916) (testimony of Brig. Gen. Enoch H. Crowder) (observing that Article of War 15 preserves the power of “the military commander in the field in time of war” to use military commissions (emphasis added)). The same urgency would not have been felt vis-À-vis enemies who had done little more than agree to violate the laws of war. Cf. 31Op. Atty. Gen. 356, 357, 361 (1918) (opining that a German spy could not be tried by military commission because, having been apprehended before entering “any camp, fortification or other military premises of the United States,” he had “committed [his offenses] outside of the field of military operations”). The Quirin Court acknowledged as much when it described the President’s authority to use law-of-war military commissions as the power to “seize and subject to disciplinary measures those enemies who in their attempt to thwart or impede our military effort have violated the law of war.” 317 U. S., at 28–29 (emphasis added).

    Winthrop and Howland are only superficially more helpful to the Government. Howland, granted, lists “conspiracy by two or more to violate the laws of war by destroying life or property in aid of the enemy” as one of over 20 “offenses against the laws and usages of war” “passed upon and punished by military commissions.” Howland 1071. But while the records of cases that Howland cites following his list of offenses against the law of war support inclusion of the other offenses mentioned, they provide no support for the inclusion of conspiracy as a violation of the law of war. See ibid. (citing Record Books of the Judge Advocate General Office, R. 2, 144; R. 3, 401, 589, 649; R. 4, 320; R. 5, 36, 590; R. 6, 20; R. 7, 413; R. 8, 529; R. 9, 149, 202, 225, 481, 524, 535; R. 10, 567; R. 11, 473, 513; R. 13, 125, 675; R. 16, 446; R. 21, 101, 280). Winthrop, apparently recognizing as much, excludes conspiracy of any kind from his own list of offenses against the law of war. See Winthrop 839–840.

    Winthrop does, unsurprisingly, include “criminal conspiracies” in his list of “[c]rimes and statutory offenses cognizable by State or U. S. courts” and triable by martial law or military government commission. See id., at 839. And, in a footnote, he cites several Civil War examples of “conspiracies of this class, or of the first and second classes combined.” Id., at 839, n. 5 (emphasis added). The Government relies on this footnote for its contention that conspiracy was triable both as an ordinary crime (a crime of the “first class”) and, independently, as a war crime (a crime of the “second class”). But the footnote will not support the weight the Government places on it.

    As we have seen, the military commissions convened during the Civil War functioned at once as martial law or military government tribunals and as law-of-war commissions. See n. 27, supra. Accordingly, they regularly tried war crimes and ordinary crimes together. Indeed, as Howland observes, “[n]ot infrequently the crime, as charged and found, was a combination of the two species of offenses.” Howland 1071; see also Davis 310, n. 2; Winthrop 842. The example he gives is “ ‘murder in violation of the laws of war.’ ” Howland 1071–1072. Winthrop’s conspiracy “of the first and second classes combined” is, like Howland’s example, best understood as a species of compound offense of the type tried by the hybrid military commissions of the Civil War. It is not a stand-alone offense against the law of war. Winthrop confirms this understanding later in his discussion, when he emphasizes that “overt acts” constituting war crimes are the only proper subject at least of those military tribunals not convened to stand in for local courts. Winthrop 841, and nn. 22, 23 (emphasis in original) (citing W. Finlason, Martial Law 130 (1867)).

    Justice Thomas cites as evidence that conspiracy is a recognized violation of the law of war the Civil War indictment against Henry Wirz, which charged the defendant with “ ‘[m]aliciously, willfully, and traitorously … combining, confederating, and conspiring [with others] to injure the health and destroy the lives of soldiers in the military service of the United States … to the end that the armies of the United States might be weakened and impaired, in violation of the laws and customs of war.’ ” Post, at 24–25 (dissenting opinion) (quoting H. R. Doc. No. 314, 55th Cong., 3d Sess., 785 (1865); emphasis deleted). As shown by the specification supporting that charge, however, Wirz was alleged to have personally committed a number of atrocities against his victims, including torture, injection of prisoners with poison, and use of “ferocious and bloodthirsty dogs” to “seize, tear, mangle, and maim the bodies and limbs” of prisoners, many of whom died as a result. Id., at 789–790. Crucially, Judge Advocate General Holt determined that one of Wirz’s alleged co-conspirators, R. B. Winder, should not be tried by military commission because there was as yet insufficient evidence of his own personal involvement in the atrocities: “[I]n the case of R. B. Winder, while the evidence at the trial of Wirz was deemed by the court to implicate him in the conspiracy against the lives of all Federal prisoners in rebel hands, no such specific overt acts of violation of the laws of war are as yet fixed upon him as to make it expedient to prefer formal charges and bring him to trial.” Id., at 783 (emphases added).37

    Finally, international sources confirm that the crime charged here is not a recognized violation of the law of war.38 As observed above, see supra, at 40, none of the major treaties governing the law of war identifies conspiracy as a violation thereof. And the only “conspiracy” crimes that have been recognized by international war crimes tribunals (whose jurisdiction often extends beyond war crimes proper to crimes against humanity and crimes against the peace) are conspiracy to commit genocide and common plan to wage aggressive war, which is a crime against the peace and requires for its commission actual participation in a “concrete plan to wage war.” 1 Trial of the Major War Criminals Before the International Military Tribunal: Nuremberg, 14 November 1945–1 October 1946, p. 225 (1947). The International Military Tribunal at Nuremberg, over the prosecution’s objections, pointedly refused to recognize as a violation of the law of war conspiracy to commit war crimes, see, e.g., 22 id., at 469,39 and convicted only Hitler’s most senior associates of conspiracy to wage aggressive war, see S. Pomorski, Conspiracy and Criminal Organization, in the Nuremberg Trial and International Law 213, 233–235 (G. Ginsburgs & V. Kudriavtsev eds. 1990). As one prominent figure from the Nuremberg trials has explained, members of the Tribunal objected to recognition of conspiracy as a violation of the law of war on the ground that “[t]he Anglo-American concept of conspiracy was not part of European legal systems and arguably not an element of the internationally recognized laws of war.” T. Taylor, Anatomy of the Nuremberg Trials: A Personal Memoir 36 (1992); see also id., at 550 (observing that Francis Biddle, who as Attorney General prosecuted the defendants in Quirin, thought the French judge had made a “ ‘persuasive argument that conspiracy in the truest sense is not known to international law’ ”).40

    In sum, the sources that the Government and Justice Thomas rely upon to show that conspiracy to violate the law of war is itself a violation of the law of war in fact demonstrate quite the opposite. Far from making the requisite substantial showing, the Government has failed even to offer a “merely colorable” case for inclusion of conspiracy among those offenses cognizable by law-of-war military commission. Cf. Quirin, 317 U. S., at 36. Because the charge does not support the commission’s jurisdiction, the commission lacks authority to try Hamdan.

    The charge’s shortcomings are not merely formal, but are indicative of a broader inability on the Executive’s part here to satisfy the most basic precondition—at least in the absence of specific congressional authorization—for establishment of military commissions: military necessity. Hamdan’s tribunal was appointed not by a military commander in the field of battle, but by a retired major general stationed away from any active hostilities. Cf. Rasul v. Bush, 542 U. S., at 487 (Kennedy, J., concurring in judgment) (observing that “Guantanamo Bay is … far removed from any hostilities”). Hamdan is charged not with an overt act for which he was caught redhanded in a theater of war and which military efficiency demands be tried expeditiously, but with an agreement the inception of which long predated the attacks of September 11, 2001 and the AUMF. That may well be a crime,41 but it is not an offense that “by the law of war may be tried by military commissio[n].” 10 U. S. C. §821. None of the overt acts alleged to have been committed in furtherance of the agreement is itself a war crime, or even necessarily occurred during time of, or in a theater of, war. Any urgent need for imposition or execution of judgment is utterly belied by the record; Hamdan was arrested in November 2001 and he was not charged until mid-2004. These simply are not the circumstances in which, by any stretch of the historical evidence or this Court’s precedents, a military commission established by Executive Order under the authority of Article 21 of the UCMJ may lawfully try a person and subject him to punishment.

VI

    Whether or not the Government has charged Hamdan with an offense against the law of war cognizable by military commission, the commission lacks power to proceed. The UCMJ conditions the President’s use of military commissions on compliance not only with the American common law of war, but also with the rest of the UCMJ itself, insofar as applicable, and with the “rules and precepts of the law of nations,” Quirin, 317 U. S., at 28—including, inter alia, the four Geneva Conventions signed in 1949. See Yamashita, 327 U. S., at 20–21, 23–24. The procedures that the Government has decreed will govern Hamdan’s trial by commission violate these laws.

A

    The commission’s procedures are set forth in Commission Order No. 1, which was amended most recently on

August 31, 2005—after Hamdan’s trial had already begun. Every commission established pursuant to Commission Order No. 1 must have a presiding officer and at least three other members, all of whom must be commissioned officers. §4(A)(1). The presiding officer’s job is to rule on questions of law and other evidentiary and interlocutory issues; the other members make findings and, if applicable, sentencing decisions. §4(A)(5). The accused is entitled to appointed military counsel and may hire civilian counsel at his own expense so long as such counsel is a U. S. citizen with security clearance “at the level SECRET or higher.” §§4(C)(2)–(3).

    The accused also is entitled to a copy of the charge(s) against him, both in English and his own language (if different), to a presumption of innocence, and to certain other rights typically afforded criminal defendants in civilian courts and courts-martial. See §§5(A)–(P). These rights are subject, however, to one glaring condition: The accused and his civilian counsel may be excluded from, and precluded from ever learning what evidence was presented during, any part of the proceeding that either the Appointing Authority or the presiding officer decides to “close.” Grounds for such closure “include the protection of information classified or classifiable … ; information protected by law or rule from unauthorized disclosure; the physical safety of participants in Commission proceedings, including prospective witnesses; intelligence and law enforcement sources, methods, or activities; and other national security interests.” §6(B)(3).42 Appointed military defense counsel must be privy to these closed sessions, but may, at the presiding officer’s discretion, be forbidden to reveal to his or her client what took place therein. Ibid.

Another striking feature of the rules governing Hamdan’s commission is that they permit the admission of any evidence that, in the opinion of the presiding officer, “would have probative value to a reasonable person.” §6(D)(1). Under this test, not only is testimonial hearsay and evidence obtained through coercion fully admissible, but neither live testimony nor witnesses’ written statements need be sworn. See §§6(D)(2)(b), (3). Moreover, the accused and his civilian counsel may be denied access to evidence in the form of “protected information” (which includes classified information as well as “information protected by law or rule from unauthorized disclosure” and “information concerning other national security interests,” §§6(B)(3), 6(D)(5)(a)(v)), so long as the presiding officer concludes that the evidence is “probative” under §6(D)(1) and that its admission without the accused’s knowledge would not “result in the denial of a full and fair trial.” §6(D)(5)(b).43 Finally, a presiding officer’s determination that evidence “would not have probative value to a reasonable person” may be overridden by a majority of the other commission members. §6(D)(1).

    Once all the evidence is in, the commission members (not including the presiding officer) must vote on the accused’s guilt. A two-thirds vote will suffice for both a verdict of guilty and for imposition of any sentence not including death (the imposition of which requires a unanimous vote). §6(F). Any appeal is taken to a three-member review panel composed of military officers and designated by the Secretary of Defense, only one member of which need have experience as a judge. §6(H)(4). The review panel is directed to “disregard any variance from procedures specified in this Order or elsewhere that would not materially have affected the outcome of the trial before the Commission.” Ibid. Once the panel makes its recommendation to the Secretary of Defense, the Secretary can either remand for further proceedings or forward the record to the President with his recommendation as to final disposition. §6(H)(5). The President then, unless he has delegated the task to the Secretary, makes the “final decision.” §6(H)(6). He may change the commission’s findings or sentence only in a manner favorable to the accused. Ibid.

B

    Hamdan raises both general and particular objections to the procedures set forth in Commission Order No. 1. His general objection is that the procedures’ admitted deviation from those governing courts-martial itself renders the commission illegal. Chief among his particular objections are that he may, under the Commission Order, be convicted based on evidence he has not seen or heard, and that any evidence admitted against him need not comply with the admissibility or relevance rules typically applicable in criminal trials and court-martial proceedings.

    The Government objects to our consideration of any procedural challenge at this stage on the grounds that (1) the abstention doctrine espoused in Councilman, 420 U. S. 738 , precludes pre-enforcement review of procedural rules, (2) Hamdan will be able to raise any such challenge following a “final decision” under the DTA, and (3) “there is … no basis to presume, before the trial has even commenced, that the trial will not be conducted in good faith and according to law.” Brief for Respondents 45–46, nn. 20–21. The first of these contentions was disposed of in Part III, supra, and neither of the latter two is sound.

    First, because Hamdan apparently is not subject to the death penalty (at least as matters now stand) and may receive a sentence shorter than 10 years’ imprisonment, he has no automatic right to review of the commission’s “final decision”44 before a federal court under the DTA. See §1005(e)(3), 119 Stat. 2743. Second, contrary to the Government’s assertion, there is a “basis to presume” that the procedures employed during Hamdan’s trial will violate the law: The procedures are described with particularity in Commission Order No. 1, and implementation of some of them has already occurred. One of Hamdan’s complaints is that he will be, and indeed already has been, excluded from his own trial. See Reply Brief for Petitioner 12; App. to Pet. for Cert. 45a. Under these circumstances, review of the procedures in advance of a “final decision”—the timing of which is left entirely to the discretion of the President under the DTA—is appropriate. We turn, then, to consider the merits of Hamdan’s procedural challenge.

C

    In part because the difference between military commissions and courts-martial originally was a difference of jurisdiction alone, and in part to protect against abuse and ensure evenhandedness under the pressures of war, the procedures governing trials by military commission historically have been the same as those governing courts-martial. See, e.g., 1 The War of the Rebellion 248 (2d series 1894) (General Order 1 issued during the Civil War required military commissions to “be constituted in a similar manner and their proceedings be conducted according to the same general rules as courts-martial in order to prevent abuses which might otherwise arise”). Accounts of commentators from Winthrop through General Crowder—who drafted Article of War 15 and whose views have been deemed “authoritative” by this Court, Madsen, 343 U. S., at 353—confirm as much.45 As recently as the Korean and Vietnam wars, during which use of military commissions was contemplated but never made, the principle of procedural parity was espoused as a background assumption. See Paust, Antiterrorism Military Commissions: Courting Illegality, 23 Mich. J. Int’l L. 1, 3–5 (2001–2002).

    There is a glaring historical exception to this general rule. The procedures and evidentiary rules used to try General Yamashita near the end of World War II deviated in significant respects from those then governing courts-martial. See 327 U. S. 1 . The force of that precedent, however, has been seriously undermined by post-World War II developments.

    Yamashita, from late 1944 until September 1945, was Commanding General of the Fourteenth Army Group of the Imperial Japanese Army, which had exercised control over the Philippine Islands. On September 3, 1945, after American forces regained control of the Philippines, Yamashita surrendered. Three weeks later, he was charged with violations of the law of war. A few weeks after that, he was arraigned before a military commission convened in the Philippines. He pleaded not guilty, and his trial lasted for two months. On December 7, 1945, Yamashita was convicted and sentenced to hang. See id., at 5; id., at 31–34 (Murphy, J., dissenting). This Court upheld the denial of his petition for a writ of habeas corpus.

    The procedures and rules of evidence employed during Yamashita’s trial departed so far from those used in courts-martial that they generated an unusually long and vociferous critique from two Members of this Court. See id., at 41–81 (Rutledge, J., joined by Murphy, J., dissenting).46 Among the dissenters’ primary concerns was that the commission had free rein to consider all evidence “which in the commission’s opinion ‘would be of assistance in proving or disproving the charge,’ without any of the usual modes of authentication.” Id., at 49 (Rutledge, J.).

    The majority, however, did not pass on the merits of Yamashita’s procedural challenges because it concluded that his status disentitled him to any protection under the Articles of War (specifically, those set forth in Article 38, which would become Article 36 of the UCMJ) or the Geneva Convention of 1929, 47 Stat. 2021 (1929 Geneva Convention). The Court explained that Yamashita was neither a “person made subject to the Articles of War by Article 2” thereof, 327 U. S., at 20, nor a protected prisoner of war being tried for crimes committed during his detention, id., at 21.

    At least partially in response to subsequent criticism of General Yamashita’s trial, the UCMJ’s codification of the Articles of War after World War II expanded the category of persons subject thereto to include defendants in Yamashita’s (and Hamdan’s) position,47 and the Third Geneva Convention of 1949 extended prisoner-of-war protections to individuals tried for crimes committed before their capture. See 3 Int’l Comm. of Red Cross,48 Commentary: Geneva Convention Relative to the Treatment of Prisoners of War 413 (1960) (hereinafter GCIII Commentary) (explaining that Article 85, which extends the Convention’s protections to “[p]risoners of war prosecuted under the laws of the Detaining Power for acts committed prior to capture,” was adopted in response to judicial interpretations of the 1929 Convention, including this Court’s decision in Yamashita). The most notorious exception to the principle of uniformity, then, has been stripped of its precedential value.

    The uniformity principle is not an inflexible one; it does not preclude all departures from the procedures dictated for use by courts-martial. But any departure must be tailored to the exigency that necessitates it. See Winthrop 835, n. 81. That understanding is reflected in Article 36 of the UCMJ, which provides:

    “(a) The procedure, including modes of proof, in cases before courts-martial, courts of inquiry, military commissions, and other military tribunals may be prescribed by the President by regulations which shall, so far as he considers practicable, apply the principles of law and the rules of evidence generally recognized in the trial of criminal cases in the United States district courts, but which may not be contrary to or inconsistent with this chapter.

    “(b) All rules and regulations made under this article shall be uniform insofar as practicable and shall be reported to Congress.” 70A Stat. 50.

    Article 36 places two restrictions on the President’s power to promulgate rules of procedure for courts-martial and military commissions alike. First, no procedural rule he adopts may be “contrary to or inconsistent with” the UCMJ—however practical it may seem. Second, the rules adopted must be “uniform insofar as practicable.” That is, the rules applied to military commissions must be the same as those applied to courts-martial unless such uniformity proves impracticable.

    Hamdan argues that Commission Order No. 1 violates both of these restrictions; he maintains that the procedures described in the Commission Order are inconsistent with the UCMJ and that the Government has offered no explanation for their deviation from the procedures governing courts-martial, which are set forth in the Manual for Courts-Martial, United States (2005 ed.) (Manual for Courts-Martial). Among the inconsistencies Hamdan identifies is that between §6 of the Commission Order, which permits exclusion of the accused from proceedings and denial of his access to evidence in certain circumstances, and the UCMJ’s requirement that “[a]ll … proceedings” other than votes and deliberations by courts-martial “shall be made a part of the record and shall be in the presence of the accused.” 10 U. S. C. A. §839(c) (Supp. 2006). Hamdan also observes that the Commission Order dispenses with virtually all evidentiary rules applicable in courts-martial.

    The Government has three responses. First, it argues, only 9 of the UCMJ’s 158 Articles—the ones that expressly mention “military commissions”49—actually apply to commissions, and Commission Order No. 1 sets forth no procedure that is “contrary to or inconsistent with” those 9 provisions. Second, the Government contends, military commissions would be of no use if the President were hamstrung by those provisions of the UCMJ that govern courts-martial. Finally, the President’s determination that “the danger to the safety of the United States and the nature of international terrorism” renders it impracticable “to apply in military commissions … the principles of law and rules of evidence generally recognized in the trial of criminal cases in the United States district courts,” November 13 Order §1(f), is, in the Government’s view, explanation enough for any deviation from court-martial procedures. See Brief for Respondents 43–47, and n. 22.

    Hamdan has the better of this argument. Without reaching the question whether any provision of Commission Order No. 1 is strictly “contrary to or inconsistent with” other provisions of the UCMJ, we conclude that the “practicability” determination the President has made is insufficient to justify variances from the procedures governing courts-martial. Subsection (b) of Article 36 was added after World War II, and requires a different showing of impracticability from the one required by subsection (a). Subsection (a) requires that the rules the President promulgates for courts-martial, provost courts, and military commissions alike conform to those that govern procedures in Article III courts, “so far as he considers practicable.” 10 U. S. C. §836(a) (emphasis added). Subsection (b), by contrast, demands that the rules applied in courts-martial, provost courts, and military commissions—whether or not they conform with the Federal Rules of Evidence—be “uniform insofar as practicable.” §836(b) (emphasis added). Under the latter provision, then, the rules set forth in the Manual for Courts-Martial must apply to military commissions unless impracticable.50

    The President here has determined, pursuant to subsection (a), that it is impracticable to apply the rules and principles of law that govern “the trial of criminal cases in the United States district courts,” §836(a), to Hamdan’s commission. We assume that complete deference is owed that determination. The President has not, however, made a similar official determination that it is impracticable to apply the rules for courts-martial.51 And even if subsection (b)’s requirements may be satisfied without such an official determination, the requirements of that subsection are not satisfied here.

    Nothing in the record before us demonstrates that it would be impracticable to apply court-martial rules in this case. There is no suggestion, for example, of any logistical difficulty in securing properly sworn and authenticated evidence or in applying the usual principles of relevance and admissibility. Assuming arguendo that the reasons articulated in the President’s Article 36(a) determination ought to be considered in evaluating the impracticability of applying court-martial rules, the only reason offered in support of that determination is the danger posed by international terrorism.52 Without for one moment underestimating that danger, it is not evident to us why it should require, in the case of Hamdan’s trial, any variance from the rules that govern courts-martial.

    The absence of any showing of impracticability is particularly disturbing when considered in light of the clear and admitted failure to apply one of the most fundamental protections afforded not just by the Manual for Courts-Martial but also by the UCMJ itself: the right to be present. See 10 U. S. C. A. §839(c) (Supp. 2006). Whether or not that departure technically is “contrary to or inconsistent with” the terms of the UCMJ, 10 U. S. C. §836(a), the jettisoning of so basic a right cannot lightly be excused as “practicable.”

    Under the circumstances, then, the rules applicable in courts-martial must apply. Since it is undisputed that Commission Order No. 1 deviates in many significant respects from those rules, it necessarily violates Article 36(b).

    The Government’s objection that requiring compliance with the court-martial rules imposes an undue burden both ignores the plain meaning of Article 36(b) and misunderstands the purpose and the history of military commissions. The military commission was not born of a desire to dispense a more summary form of justice than is afforded by courts-martial; it developed, rather, as a tribunal of necessity to be employed when courts-martial lacked jurisdiction over either the accused or the subject matter. See Winthrop 831. Exigency lent the commission its legitimacy, but did not further justify the wholesale jettisoning of procedural protections. That history explains why the military commission’s procedures typically have been the ones used by courts-martial. That the jurisdiction of the two tribunals today may sometimes overlap, see Madsen, 343 U. S., at 354, does not detract from the force of this history;53 Article 21 did not transform the military commission from a tribunal of true exigency into a more convenient adjudicatory tool. Article 36, confirming as much, strikes a careful balance between uniform procedure and the need to accommodate exigencies that may sometimes arise in a theater of war. That Article not having been complied with here, the rules specified for Hamdan’s trial are illegal.54

D

    The procedures adopted to try Hamdan also violate the Geneva Conventions. The Court of Appeals dismissed Hamdan’s Geneva Convention challenge on three independent grounds: (1) the Geneva Conventions are not judicially enforceable; (2) Hamdan in any event is not entitled to their protections; and (3) even if he is entitled to their protections, Councilman abstention is appropriate. Judge Williams, concurring, rejected the second ground but agreed with the majority respecting the first and the last. As we explained in Part III, supra, the abstention rule applied in Councilman, 420 U. S. 738 , is not applicable here.55 And for the reasons that follow, we hold that neither of the other grounds the Court of Appeals gave for its decision is persuasive.

i

    The Court of Appeals relied on Johnson v. Eisentrager, 339 U. S. 763 (1950) , to hold that Hamdan could not invoke the Geneva Conventions to challenge the Government’s plan to prosecute him in accordance with Commission Order No. 1. Eisentrager involved a challenge by 21 German nationals to their 1945 convictions for war crimes by a military tribunal convened in Nanking, China, and to their subsequent imprisonment in occupied Germany. The petitioners argued, inter alia, that the 1929 Geneva Convention rendered illegal some of the procedures employed during their trials, which they said deviated impermissibly from the procedures used by courts-martial to try American soldiers. See id., at 789. We rejected that claim on the merits because the petitioners (unlike Hamdan here) had failed to identify any prejudicial disparity “between the Commission that tried [them] and those that would try an offending soldier of the American forces of like rank,” and in any event could claim no protection, under the 1929 Convention, during trials for crimes that occurred before their confinement as prisoners of war. Id., at 790.56

    Buried in a footnote of the opinion, however, is this curious statement suggesting that the Court lacked power even to consider the merits of the Geneva Convention argument:

“We are not holding that these prisoners have no right which the military authorities are bound to respect. The United States, by the Geneva Convention of July 27, 1929, 47 Stat. 2021, concluded with forty-six other countries, including the German Reich, an agreement upon the treatment to be accorded captives. These prisoners claim to be and are entitled to its protection. It is, however, the obvious scheme of the Agreement that responsibility for observance and enforcement of these rights is upon political and military authorities. Rights of alien enemies are vindicated under it only through protests and intervention of protecting powers as the rights of our citizens against foreign governments are vindicated only by Presidential intervention.” Id., at 789, n. 14.

The Court of Appeals, on the strength of this footnote, held that “the 1949 Geneva Convention does not confer upon Hamdan a right to enforce its provisions in court.” 415 F. 3d, at 40.

    Whatever else might be said about the Eisentrager footnote, it does not control this case. We may assume that “the obvious scheme” of the 1949 Conventions is identical in all relevant respects to that of the 1929 Convention,57 and even that that scheme would, absent some other provision of law, preclude Hamdan’s invocation of the Convention’s provisions as an independent source of law binding the Government’s actions and furnishing petitioner with any enforceable right.58 For, regardless of the nature of the rights conferred on Hamdan, cf. United States v. Rauscher, 119 U. S. 407 (1886) , they are, as the Government does not dispute, part of the law of war. See Hamdi, 542 U. S., at 520–521 (plurality opinion). And compliance with the law of war is the condition upon which the authority set forth in Article 21 is granted.

ii

    For the Court of Appeals, acknowledgment of that condition was no bar to Hamdan’s trial by commission. As an alternative to its holding that Hamdan could not invoke the Geneva Conventions at all, the Court of Appeals concluded that the Conventions did not in any event apply to the armed conflict during which Hamdan was captured. The court accepted the Executive’s assertions that Hamdan was captured in connection with the United States’ war with al Qaeda and that that war is distinct from the war with the Taliban in Afghanistan. It further reasoned that the war with al Qaeda evades the reach of the Geneva Conventions. See 415 F. 3d, at 41–42. We, like Judge Williams, disagree with the latter conclusion.

    The conflict with al Qaeda is not, according to the Government, a conflict to which the full protections afforded detainees under the 1949 Geneva Conventions apply because Article 2 of those Conventions (which appears in all four Conventions) renders the full protections applicable only to “all cases of declared war or of any other armed conflict which may arise between two or more of the High Contracting Parties.” 6 U. S. T., at 3318.59 Since Hamdan was captured and detained incident to the conflict with al Qaeda and not the conflict with the Taliban, and since al Qaeda, unlike Afghanistan, is not a “High Contracting Party”—i.e., a signatory of the Conventions, the protections of those Conventions are not, it is argued, applicable to Hamdan.60

    We need not decide the merits of this argument because there is at least one provision of the Geneva Conventions that applies here even if the relevant conflict is not one between signatories.61 Article 3, often referred to as Common Article 3 because, like Article 2, it appears in all four Geneva Conventions, provides that in a “conflict not of an international character occurring in the territory of one of the High Contracting Parties, each Party62 to the conflict shall be bound to apply, as a minimum,” certain provisions protecting “[p]ersons taking no active part in the hostilities, including members of armed forces who have laid down their arms and those placed hors de combat by … detention.” Id., at 3318. One such provision prohibits “the passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court affording all the judicial guarantees which are recognized as indispensable by civilized peoples.” Ibid.

    The Court of Appeals thought, and the Government asserts, that Common Article 3 does not apply to Hamdan because the conflict with al Qaeda, being “ ‘international in scope,’ ” does not qualify as a “ ‘conflict not of an international character.’ ” 415 F. 3d, at 41. That reasoning is erroneous. The term “conflict not of an international character” is used here in contradistinction to a conflict between nations. So much is demonstrated by the “fundamental logic [of] the Convention’s provisions on its application.” Id., at 44 (Williams, J., concurring). Common Article 2 provides that “the present Convention shall apply to all cases of declared war or of any other armed conflict which may arise between two or more of the High Contracting Parties.” 6 U. S. T., at 3318 (Art. 2, ¶1). High Contracting Parties (signatories) also must abide by all terms of the Conventions vis-À-vis one another even if one party to the conflict is a nonsignatory “Power,” and must so abide vis-À-vis the nonsignatory if “the latter accepts and applies” those terms. Ibid. (Art. 2, ¶3). Common Article 3, by contrast, affords some minimal protection, falling short of full protection under the Conventions, to individuals associated with neither a signatory nor even a nonsignatory “Power” who are involved in a conflict “in the territory of” a signatory. The latter kind of conflict is distinguishable from the conflict described in Common Article 2 chiefly because it does not involve a clash between nations (whether signatories or not). In context, then, the phrase “not of an international character” bears its literal meaning. See, e.g., J. Bentham, Introduction to the Principles of Morals and Legislation 6, 296 (J. Burns & H. Hart eds. 1970) (using the term “international law” as a “new though not inexpressive appellation” meaning “betwixt nation and nation”; defining “international” to include “mutual transactions between sovereigns as such”); Commentary on the Additional Protocols to the Geneva Conventions of 12 August 1949, p. 1351 (1987) (“[A] non-international armed conflict is distinct from an international armed conflict because of the legal status of the entities opposing each other”).

    Although the official commentaries accompanying Common Article 3 indicate that an important purpose of the provision was to furnish minimal protection to rebels involved in one kind of “conflict not of an international character,” i.e., a civil war, see GCIII Commentary 36–37, the commentaries also make clear “that the scope of the Article must be as wide as possible,” id., at 36.63 In fact, limiting language that would have rendered Common Article 3 applicable “especially [to] cases of civil war, colonial conflicts, or wars of religion,” was omitted from the final version of the Article, which coupled broader scope of application with a narrower range of rights than did earlier proposed iterations. See GCIII Commentary 42–43.

iii

    Common Article 3, then, is applicable here and, as indicated above, requires that Hamdan be tried by a “regularly constituted court affording all the judicial guarantees which are recognized as indispensable by civilized peoples.” 6 U. S. T., at 3320 (Art. 3, ¶1(d)). While the term “regularly constituted court” is not specifically defined in either Common Article 3 or its accompanying commentary, other sources disclose its core meaning. The commentary accompanying a provision of the Fourth Geneva Convention, for example, defines “ ‘regularly constituted’ ” tribunals to include “ordinary military courts” and “definitely exclud[e] all special tribunals.” GCIV Commentary 340 (defining the term “properly constituted” in Article 66, which the commentary treats as identical to “regularly constituted”);64 see also Yamashita, 327 U. S., at 44 (Rutledge, J., dissenting) (describing military commission as a court “specially constituted for a particular trial”). And one of the Red Cross’ own treatises defines “regularly constituted court” as used in Common Article 3 to mean “established and organized in accordance with the laws and procedures already in force in a country.” Int’l Comm. of Red Cross, 1 Customary International Humanitarian Law 355 (2005); see also GCIV Commentary 340 (observing that “ordinary military courts” will “be set up in accordance with the recognized principles governing the administration of justice”).

    The Government offers only a cursory defense of Hamdan’s military commission in light of Common Article 3. See Brief for Respondents 49–50. As Justice Kennedy explains, that defense fails because “[t]he regular military courts in our system are the courts-martial established by

congressional statutes.” Post, at 8 (opinion concurring in part). At a minimum, a military commission “can be ‘regularly constituted’ by the standards of our military justice system only if some practical need explains deviations from court-martial practice.” Post, at 10. As we have explained, see Part VI–C, supra, no such need has been demonstrated here.65

iv

    Inextricably intertwined with the question of regular constitution is the evaluation of the procedures governing the tribunal and whether they afford “all the judicial guarantees which are recognized as indispensable by civilized peoples.” 6 U. S. T., at 3320 (Art. 3, ¶1(d)). Like the phrase “regularly constituted court,” this phrase is not defined in the text of the Geneva Conventions. But it must be understood to incorporate at least the barest of those trial protections that have been recognized by customary international law. Many of these are described in Article 75 of Protocol I to the Geneva Conventions of 1949, adopted in 1977 (Protocol I). Although the United States declined to ratify Protocol I, its objections were not to Article 75 thereof. Indeed, it appears that the Government “regard[s] the provisions of Article 75 as an articulation of safeguards to which all persons in the hands of an enemy are entitled.” Taft, The Law of Armed Conflict After 9/11: Some Salient Features, 28 Yale J. Int’l L. 319, 322 (2003). Among the rights set forth in Article 75 is the “right to be tried in [one’s] presence.” Protocol I, Art. 75(4)(e).66

    We agree with Justice Kennedy that the procedures adopted to try Hamdan deviate from those governing courts-martial in ways not justified by any “evident practical need,” post, at 11, and for that reason, at least, fail to afford the requisite guarantees. See post, at 8, 11–17. We add only that, as noted in Part VI–A, supra, various provisions of Commission Order No. 1 dispense with the principles, articulated in Article 75 and indisputably part of the customary international law, that an accused must, absent disruptive conduct or consent, be present for his trial and must be privy to the evidence against him. See §§6(B)(3), (D).67 That the Government has a compelling interest in denying Hamdan access to certain sensitive information is not doubted. Cf. post, at 47–48 (Thomas, J., dissenting). But, at least absent express statutory provision to the contrary, information used to convict a person of a crime must be disclosed to him.

v

    Common Article 3 obviously tolerates a great degree of flexibility in trying individuals captured during armed conflict; its requirements are general ones, crafted to accommodate a wide variety of legal systems. But requirements they are nonetheless. The commission that the President has convened to try Hamdan does not meet those requirements.

VII

    We have assumed, as we must, that the allegations made in the Government’s charge against Hamdan are true. We have assumed, moreover, the truth of the message implicit in that charge—viz., that Hamdan is a dangerous individual whose beliefs, if acted upon, would cause great harm and even death to innocent civilians, and who would act upon those beliefs if given the opportunity. It bears emphasizing that Hamdan does not challenge, and we do not today address, the Government’s power to detain him for the duration of active hostilities in order to prevent such harm. But in undertaking to try Hamdan and subject him to criminal punishment, the Executive is bound to comply with the Rule of Law that prevails in this jurisdiction.

    The judgment of the Court of Appeals is reversed, and the case is remanded for further proceedings.

It is so ordered.

The Chief Justice took no part in the consideration or decision of this case.


Notes

1 An “enemy combatant” is defined by the military order as “an individual who was part of or supporting Taliban or al Qaeda forces, or associated forces that are engaged in hostilities against the United States or its coalition partners.” Memorandum from Deputy Secretary of Defense Paul Wolfowitz re: Order Establishing Combatant Status Review Tribunal §a (Jul. 7, 2004), available at http://www.defenselink.mil/news/Jul2004/d20040707review.pdf (all Internet materials as visited June 26, 2006, and available in Clerk of Court’s case file).

2 The military order referenced in this section is discussed further in Parts III and VI, infra.

3 The penultimate subsections of §1005 emphasize that the provision does not “confer any constitutional right on an alien detained as an enemy combatant outside the United States” and that the “United States” does not, for purposes of §1005, include Guantanamo Bay. §§1005(f)–(g).

4 “ ‘And be it further enacted, That so much of the act approved February 5, 1867, entitled “An act to amend an act to establish the judicial courts of the United States, approved September 24, 1789,” as authorized an appeal from the judgment of the Circuit Court to the Supreme Court of the United States, or the exercise of any such jurisdiction by said Supreme Court, on appeals which have been, or may hereafter be taken, be, and the same is hereby repealed.’ ” 7 Wall., at 508.

5 See Hughes Aircraft Co. v. United States ex rel. Schumer, 520 U. S. 939, 951 (1997) (“The fact that courts often apply newly enacted jurisdiction-allocating statutes to pending cases merely evidences certain limited circumstances failing to meet the conditions for our generally applicable presumption against retroactivity …”).

6 Cf. Hughes Aircraft, 520 U. S., at 951 (“Statutes merely addressing which court shall have jurisdiction to entertain a particular cause of action can fairly be said merely to regulate the secondary conduct of litigation and not the underlying primary conduct of the parties” (emphasis in original)).

7 In his insistence to the contrary, Justice Scalia reads too much into Bruner v. United States, 343 U. S. 112 (1952) , Hallowell v. Commons, 239 U. S. 506 (1916) , and Insurance Co. v. Ritchie, 5Wall. 541 (1867). See post, at 2–4 (dissenting opinion). None of those cases says that the absence of an express provision reserving jurisdiction over pending cases trumps or renders irrelevant any other indications of congressional intent. Indeed, Bruner itself relied on such other indications–including a negative inference drawn from the statutory text, cf. infra, at 13–to support its conclusion that jurisdiction was not available. The Court observed that (1) Congress had been put on notice by prior lower court cases addressing the Tucker Act that it ought to specifically reserve jurisdiction over pending cases, see 343 U. S., at 115, and (2) in contrast to the congressional silence concerning reservation of jurisdiction, reservation had been made of “ ‘any rights or liabilities’ existing at the effective date of the Act” repealed by another provision of the Act, ibid., n. 7.

8 The question in Lindh was whether new limitations on the availability of habeas relief imposed by the Antiterrorism and Effective Death Penalty Act of 1996 (AEDPA), 110 Stat. 1214, applied to habeas actions pending on the date of AEDPA’s enactment. We held that they did not. At the outset, we rejected the State’s argument that, in the absence of a clear congressional statement to the contrary, a “procedural” rule must apply to pending cases. 521 U. S., at 326.

9 That paragraph (1), along with paragraphs (2) and (3), is to “take effect on the date of enactment,” DTA §1005(h)(1), 119 Stat. 2743, is not dispositive; “a ‘statement that a statute will become effective on a certain date does not even arguably suggest that it has any application to conduct that occurred at an earlier date.’ ” INS v. St. Cyr, 533 U. S. 289, 317 (2001) (quoting Landgraf v. USI Film Products, 511 U. S. 244, 257 (1994) ). Certainly, the “effective date” provision cannot bear the weight Justice Scalia would place on it. See post, at 5, and n. 1. Congress deemed that provision insufficient, standing alone, to render subsections (e)(2) and (e)(3) applicable to pending cases; hence its adoption of subsection (h)(2). Justice Scalia seeks to avoid reducing subsection (h)(2) to a mere redundancy—a consequence he seems to acknowledge must otherwise follow from his interpretation—by speculating that Congress had special reasons, not also relevant to subsection (e)(1), to worry that subsections (e)(2) and (e)(3) would be ruled inapplicable to pending cases. As we explain infra, at 17, and n. 12, that attempt fails.

10 We note that statements made by Senators preceding passage of the Act lend further support to what the text of the DTA and its drafting history already make plain. Senator Levin, one of the sponsors of the final bill, objected to earlier versions of the Act’s “effective date” provision that would have made subsection (e)(1) applicable to pending cases. See, e.g., 151 Cong. Rec. S12667 (Nov. 10, 2005) (amendment proposed by Sen. Graham that would have rendered what is now subsection (e)(1) applicable to “any application or other action that is pending on or after the date of the enactment of this Act”). Senator Levin urged adoption of an alternative amendment that “would apply only to new habeas cases filed after the date of enactment.” Id., at S12802 (Nov. 15, 2005). That alternative amendment became the text of subsection (h)(2). (In light of the extensive discussion of the DTA’s effect on pending cases prior to passage of the Act, see, e.g., id., at S12664 (Nov. 10, 2005); id., at S12755 (Nov. 14, 2005); id., at S12799–S12802 (Nov. 15, 2005); id., at S14245, S14252–S14253, S14257–S14258, S14274–S14275 (Dec. 21, 2005), it cannot be said that the changes to subsection (h)(2) were inconsequential. Cf. post, at 14 (Scalia, J., dissenting).) While statements attributed to the final bill’s two other sponsors, Senators Graham and Kyl, arguably contradict Senator Levin’s contention that the final version of the Act preserved jurisdiction over pending habeas cases, see 151 Cong. Rec. S14263–S14264 (Dec. 21, 2005), those statements appear to have been inserted into the Congressional Record after the Senate debate. See Reply Brief for Petitioner 5, n. 6; see also 151 Cong. Rec. S14260 (statement of Sen. Kyl) (“I would like to say a few words about the now-completed National Defense Authorization Act for fiscal year 2006” (emphasis added)). All statements made during the debate itself support Senator Levin’s understanding that the final text of the DTA would not render subsection (e)(1) applicable to pending cases. See, e.g., id., at S14245, S14252–S14253, S14274–S14275 (Dec. 21, 2005). The statements that Justice Scalia cites as evidence to the contrary construe subsection (e)(3) to strip this Court of jurisdiction, see post, at 12, n. 4 (dissenting opinion) (quoting 151 Cong. Rec. S12796 (Nov. 15, 2005) (statement of Sen. Specter))—a construction that the Government has expressly disavowed in this litigation, see n. 11, infra. The inapposite November 14, 2005, statement of Senator Graham, which Justice Scalia cites as evidence of that Senator’s “assumption that pending cases are covered,” post, at 12, and n. 3 (citing 151 Cong. Rec. S12756 (Nov. 14, 2005)), follows directly after the uncontradicted statement of his co-sponsor, Senator Levin, assuring members of the Senate that “the amendment will not strip the courts of jurisdiction over [pending] cases.” Id., at S12755.

11 The District of Columbia Circuit’s jurisdiction, while “exclusive” in one sense, would not bar this Court’s review on appeal from a decision under the DTA. See Reply Brief in Support of Respondents’ Motion to Dismiss 16–17, n. 12 (“While the DTA does not expressly call for Supreme Court review of the District of Columbia Circuit’s decisions, Section 1005(e)(2) and (3) … do not remove this Court’s jurisdiction over such decisions under 28 U. S. C. §1254(1)”).

12 This assertion is itself highly questionable. The cases that Justice Scalia cites to support his distinction are Republic of Austria v. Altmann, 541 U. S. 677 (2004) , and Hughes Aircraft Co. v. United States ex rel. Schumer, 520 U. S. 939 (1997) . See post, at 8. While the Court in both of those cases recognized that statutes “creating” jurisdiction may have retroactive effect if they affect “substantive” rights, see Altmann, 541 U. S., at 695, and n. 15; Hughes Aircraft, 520 U. S., at 951, we have applied the same analysis to statutes that have jurisdiction-stripping effect, see Lindh v. Murphy, 521 U. S. 320, 327–328 (1997) ; id., at 342–343 (Rehnquist, C. J., dissenting) (construing AEDPA’s amendments as “ousting jurisdiction”).

13 See Landgraf, 511 U. S., at 271, n. 25 (observing that “the great majority of our decisions relying upon the antiretroactivity presumption have involved intervening statutes burdening private parties,” though “we have applied the presumption in cases involving new monetary obligations that fell only on the government” (emphasis added)); see also Altmann, 541 U. S., at 728–729 (Kennedy, J., dissenting) (explaining that if retroactivity concerns do not arise when a new monetary obligation is imposed on the United States it is because “Congress, by virtue of authoring the legislation, is itself fully capable of protecting the Federal Government from having its rights degraded by retroactive laws”).

14 There may be habeas cases that were pending in the lower courts at the time the DTA was enacted that do qualify as challenges to “final decision[s]” within the meaning of subsection (e)(2) or (e)(3). We express no view about whether the DTA would require transfer of such an action to the District of Columbia Circuit.

15 Because we conclude that §1005(e)(1) does not strip federal courts’ jurisdiction over cases pending on the date of the DTA’s enactment, we do not decide whether, if it were otherwise, this Court would nonetheless retain jurisdiction to hear Hamdan’s appeal. Cf. supra, at 10. Nor do we decide the manner in which the canon of constitutional avoidance should affect subsequent interpretation of the DTA. See, e.g., St. Cyr, 533 U. S., at 300 (a construction of a statute “that would entirely preclude review of a pure question of law by any court would give rise to substantial constitutional questions”).

16 Councilman distinguished service personnel from civilians, whose challenges to ongoing military proceedings are cognizable in federal court. See, e.g., United States ex rel. Toth v. Quarles, 350 U. S. 11 (1955) . As we explained in Councilman, abstention is not appropriate in cases in which individuals raise “ ‘substantial arguments denying the right of the military to try them at all,’ ” and in which the legal challenge “turn[s] on the status of the persons as to whom the military asserted its power.” 420 U. S., at 759 (quoting Noyd v. Bond, 395 U. S. 683 , n. 8 (1969)). In other words, we do not apply Councilman abstention when there is a substantial question whether a military tribunal has personal jurisdiction over the defendant. Because we conclude that abstention is inappropriate for a more basic reason, we need not consider whether the jurisdictional exception recognized in Councilman applies here.

17 See also Noyd, 395 U. S., at 694–696 (noting that the Court of Military Appeals consisted of “disinterested civilian judges,” and concluding that there was no reason for the Court to address an Air Force Captain’s argument that he was entitled to remain free from confinement pending appeal of his conviction by court-martial “when the highest military court stands ready to consider petitioner’s arguments”). Cf. Parisi v. Davidson, 405 U. S. 34, 41–43 (1972) (“Under accepted principles of comity, the court should stay its hand only if the relief the petitioner seeks … would also be available to him with reasonable promptness and certainty through the machinery of the military judicial system in its processing of the court-martial charge”).

18 If he chooses, the President may delegate this ultimate decisionmaking authority to the Secretary of Defense. See §6(H)(6).

19 Justice Scalia chides us for failing to include the District of Columbia Circuit’s review powers under the DTA in our description of the review mechanism erected by Commission Order No. 1. See post, at 22. Whether or not the limited review permitted under the DTA may be treated as akin to the plenary review exercised by the Court of Appeals for the Armed Forces, petitioner here is not afforded a right to such review. See infra, at 52; §1005(e)(3), 119 Stat. 2743.

20 Having correctly declined to abstain from addressing Hamdan’s challenge to the lawfulness of the military commission convened to try him, the Court of Appeals suggested that Councilman abstention nonetheless applied to bar its consideration of one of Hamdan’s arguments—namely, that his commission violated Article 3 of the Third Geneva Convention, 6 U. S. T. 3316, 3318. See Part VI, infra. Although the Court of Appeals rejected the Article 3 argument on the merits, it also stated that, because the challenge was not “jurisdictional,” it did not fall within the exception that Schlesinger v. Councilman, 420 U. S. 738 (1975) , recognized for defendants who raise substantial arguments that a military tribunal lacks personal jurisdiction over them. See 415 F. 3d, at 42. In reaching this conclusion, the Court of Appeals conflated two distinct inquiries: (1) whether Hamdan has raised a substantial argument that the military commission lacks authority to try him; and, more fundamentally, (2) whether the comity considerations underlying Councilman apply to trigger the abstention principle in the first place. As the Court of Appeals acknowledged at the beginning of its opinion, the first question warrants consideration only if the answer to the second is yes. See 415 F. 3d, at 36–37. Since, as the Court of Appeals properly concluded, the answer to the second question is in fact no, there is no need to consider any exception. At any rate, it appears that the exception would apply here. As discussed in Part VI, infra, Hamdan raises a substantial argument that, because the military commission that has been convened to try him is not a “ ‘regularly constituted court’ ” under the Geneva Conventions, it is ultra vires and thus lacks jurisdiction over him. Brief for Petitioner 5.

21 See also Winthrop 831 (“[I]n general, it is those provisions of the Constitution which empower Congress to ‘declare war’ and ‘raise armies,’ and which, in authorizing the initiation of war, authorize the employment of all necessary and proper agencies for its due prosecution, from which this tribunal derives its original sanction” (emphasis in original)).

22 Article 15 was first adopted as part of the Articles of War in 1916. See Act of Aug. 29, 1916, ch. 418, §3, Art. 15, 39 Stat. 652. When the Articles of War were codified and re-enacted as the UCMJ in 1950, Congress determined to retain Article 15 because it had been “construed by the Supreme Court (Ex Parte Quirin, 317 U. S. 1 (1942) ).” S. Rep. No. 486, 81st Cong., 1st Sess., 13 (1949).

23 Whether or not the President has independent power, absent congressional authorization, to convene military commissions, he may not disregard limitations that Congress has, in proper exercise of its own war powers, placed on his powers. See Youngstown Sheet & Tube Co. v. Sawyer, 343 U. S. 579, 637 (1952) (Jackson, J., concurring). The Government does not argue otherwise.

24 On this point, it is noteworthy that the Court in Ex parte Quirin, 317 U. S. 1 (1942) , looked beyond Congress’ declaration of war and accompanying authorization for use of force during World War II, and relied instead on Article of War 15 to find that Congress had authorized the use of military commissions in some circumstances. See id., at 26–29. Justice Thomas’ assertion that we commit “error” in reading Article 21 of the UCMJ to place limitations upon the President’s use of military commissions, see post, at 5 (dissenting opinion), ignores the reasoning in Quirin.

25 The justification for, and limitations on, these commissions were summarized in Milligan: “If, in foreign invasion or civil war, the courts are actually closed, and it is impossible to administer criminal justice according to law, then, on the theatre of active military operations, where war really prevails, there is a necessity to furnish a substitute for the civil authority, thus overthrown, to preserve the safety of the army and society; and as no power is left but the military, it is allowed to govern by martial rule until the laws can have their free course. As necessity creates the rule, so it limits its duration; for, if this government is continued after the courts are reinstated, it is a gross usurpation of power. Martial rule can never exist where the courts are open, and in the proper and unobstructed exercise of their jurisdiction. It is also confined to the locality of actual war.” 4 Wall., at 127 (emphases in original).

26 The limitations on these occupied territory or military government commissions are tailored to the tribunals’ purpose and the exigencies that necessitate their use. They may be employed “pending the establishment of civil government,” Madsen, 343 U. S., at 354–355, which may in some cases extend beyond the “cessation of hostilities,” id., at 348.

27 So much may not be evident on cold review of the Civil War trials often cited as precedent for this kind of tribunal because the commissions established during that conflict operated as both martial law or military government tribunals and law-of-war commissions. Hence, “military commanders began the practice [during the Civil War] of using the same name, the same rules, and often the same tribunals” to try both ordinary crimes and war crimes. Bickers, 34 Tex. Tech. L. Rev., at 908. “For the first time, accused horse thieves and alleged saboteurs found themselves subject to trial by the same military commission.” Id., at 909. The Civil War precedents must therefore be considered with caution; as we recognized in Quirin, 317 U. S., at 29, and as further discussed below, commissions convened during time of war but under neither martial law nor military government may try only offenses against the law of war.

28 If the commission is established pursuant to martial law or military government, its jurisdiction extends to offenses committed within “the exercise of military government or martial law.” Winthrop 837.

29 Winthrop adds as a fifth, albeit not-always-complied-with, criterion that “the trial must be had within the theatre of war . . . ; that, if held elsewhere, and where the civil courts are open and available, the proceedings and sentence will be coram non judice.” Id., at 836. The Government does not assert that Guantanamo Bay is a theater of war, but instead suggests that neither Washington, D. C., in 1942 nor the Philippines in 1945 qualified as a “war zone” either. Brief for Respondents 27; cf. Quirin, 317 U. S. 1 ; In re Yamashita, 327 U. S. 1 (1946) .

30 The elements of this conspiracy charge have been defined not by Congress but by the President. See Military Commission Instruction No. 2, 32 CFR §11.6 (2005).

31 Justice Thomas would treat Osama bin Laden’s 1996 declaration of jihad against Americans as the inception of the war. See post, at 7–10 (dissenting opinion). But even the Government does not go so far; although the United States had for some time prior to the attacks of September 11, 2001, been aggressively pursuing al Qaeda, neither in the charging document nor in submissions before this Court has the Government asserted that the President’s war powers were activated prior to September 11, 2001. Cf. Brief for Respondents 25 (describing the events of September 11, 2001, as “an act of war” that “triggered a right to deploy military forces abroad to defend the United States by combating al Qaeda”). Justice Thomas’ further argument that the AUMF is “backward looking” and therefore authorizes trial by military commission of crimes that occurred prior to the inception of war is insupportable. See post, at 8, n. 3. If nothing else, Article 21 of the UCMJ requires that the President comply with the law of war in his use of military commissions. As explained in the text, the law of war permits trial only of offenses “committed within the period of the war.” Winthrop 837; see also Quirin, 317 U. S., at 28–29 (observing that law-of-war military commissions may be used to try “those enemies who in their attempt to thwart or impede our military effort have violated the law of war” (emphasis added)). The sources that Justice Thomas relies on to suggest otherwise simply do not support his position. Colonel Green’s short exegesis on military commissions cites Howland for the proposition that “[o]ffenses committed before a formal declaration of war or before the declaration of martial law may be tried by military commission.” The Military Commission, 42 Am. J. Int’l L. 832, 848 (1948) (emphases added) (cited post, at 9–10). Assuming that to be true, nothing in our analysis turns on the admitted absence of either a formal declaration of war or a declaration of martial law. Our focus instead is on the September 11, 2001 attacks that the Government characterizes as the relevant “act[s] of war,” and on the measure that authorized the President’s deployment of military force—the AUMF. Because we do not question the Government’s position that the war commenced with the events of September 11, 2001, the Prize Cases, 2Black 635 (1863) (cited post, at 2, 7, 8, and 10 (Thomas, J., dissenting)), are not germane to the analysis. Finally, Justice Thomas’ assertion that Julius Otto Kuehn’s trial by military commission “for conspiring with Japanese officials to betray the United States fleet to the Imperial Japanese Government prior to its attack on Pearl Harbor” stands as authoritative precedent for Hamdan’s trial by commission, post, at 9, misses the mark in three critical respects. First, Kuehn was tried for the federal espionage crimes under what were then 50 U. S C. §§31, 32, and 34, not with common-law violations of the law of war. See Hearings before the Joint Committee on the Investigation of the Pearl Harbor Attack, 79th Cong., 1st Sess., pt. 30, pp. 3067–3069 (1946). Second, he was tried by martial law commission (a kind of commission Justice Thomas acknowledges is not relevant to the analysis here, and whose jurisdiction extends to offenses committed within “the exercise of . . . martial law,” Winthrop 837, see supra, n. 28), not a commission established exclusively to try violations of the law of war. See ibid. Third, the martial law commissions established to try crimes in Hawaii were ultimately declared illegal by this Court. See Duncan v. Kahanamoku, 327 U. S. 304, 324 (1946) (“The phrase ‘martial law’ as employed in [the Hawaiian Organic Act], while intended to authorize the military to act vigorously for the maintenance of an orderly civil government and for the defense of the Islands against actual or threatened rebellion or invasion, was not intended to authorize the supplanting of courts by military tribunals”).

32 Justice Thomas adopts the remarkable view, not advocated by the Government, that the charging document in this case actually includes more than one charge: Conspiracy and several other ill-defined crimes, like “joining an organization” that has a criminal purpose, “ ‘[b]eing a guerilla,’ ” and aiding the enemy. See post, at 16–21, and n. 9. There are innumerable problems with this approach. First, the crimes Justice Thomas identifies were not actually charged. It is one thing to observe that charges before a military commission “ ‘need not be stated with the precision of a common law indictment,’ ” post, at 15, n. 7 (citation omitted); it is quite another to say that a crime not charged may nonetheless be read into an indictment. Second, the Government plainly had available to it the tools and the time it needed to charge petitioner with the various crimes Justice Thomas refers to, if it believed they were supported by the allegations. As Justice Thomas himself observes, see post, at 21, the crime of aiding the enemy may, in circumstances where the accused owes allegiance to the party whose enemy he is alleged to have aided, be triable by military commission pursuant to Article 104 of the UCMJ, 10 U. S. C. §904. Indeed, the Government has charged detainees under this provision when it has seen fit to do so. See Brief for David Hicks as Amicus Curiae 7. Third, the cases Justice Thomas relies on to show that Hamdan may be guilty of violations of the law of war not actually charged do not support his argument. Justice Thomas begins by blurring the distinction between those categories of “offender” who may be tried by military commission (e.g., jayhawkers and the like) with the “offenses” that may be so tried. Even when it comes to “ ‘being a guerilla,’ ” cf. post, at 18, n. 9 (citation omitted), a label alone does not render a person susceptible to execution or other criminal punishment; the charge of “ ‘being a guerilla’ ” invariably is accompanied by the allegation that the defendant “ ‘took up arms’ ” as such. This is because, as explained by Judge Advocate General Holt in a decision upholding the charge of “ ‘being a guerilla’ ” as one recognized by “the universal usage of the times,” the charge is simply shorthand (akin to “being a spy”) for “the perpetration of a succession of similar acts” of violence. Record Books of the Judge Advocate General Office, R. 3, 590. The sources cited by Justice Thomas confirm as much. See cases cited post, at 18, n. 9. Likewise, the suggestion that the Nuremberg precedents support Hamdan’s conviction for the (uncharged) crime of joining a criminal organization must fail. Cf. post, at 19–21. The convictions of certain high-level Nazi officials for “membership in a criminal organization” were secured pursuant to specific provisions of the Charter of the International Military Tribunal that permitted indictment of individual organization members following convictions of the organizations themselves. See Arts. 9 and 10, in 1 Trial of the Major War Criminals Before the International Military Tribunal 12 (1947). The initial plan to use organizations’ convictions as predicates for mass individual trials ultimately was abandoned. See T. Taylor, Anatomy of the Nuremberg Trials: A Personal Memoir 584–585, 638 (1992).

33 Cf. 10 U. S. C. §904 (making triable by military commission the crime of aiding the enemy); §906 (same for spying); War Crimes Act of 1996, 18 U. S. C. §2441 (2000 ed. and Supp. III) (listing war crimes); Foreign Operations, Export Financing, and Related Appropriations Act, 1998, §583, 111 Stat. 2436 (same).

34 While the common law necessarily is “evolutionary in nature,” post, at 13 (Thomas, J., dissenting), even in jurisdictions where common law crimes are still part of the penal framework, an act does not become a crime without its foundations having been firmly established in precedent. See, e.g., R. v. Rimmington, [2006] 2 All E. R. 257, 275–279 (House of Lords); id., at 279 (while “some degree of vagueness is inevitable and development of the law is a recognised feature of common law courts, … the law-making function of the courts must remain within reasonable limits”); see also Rogers v. Tennessee, 532 U. S. 451, 472–478 (2001) (Scalia, J., dissenting). The caution that must be exercised in the incremental development of common-law crimes by the judiciary is, for the reasons explained in the text, all the more critical when reviewing developments that stem from military action.

35 The 19th-century trial of the “Lincoln conspirators,” even if properly classified as a trial by law-of-war commission, cf. W. Rehnquist, All the Laws But One: Civil Liberties in Wartime 165–167 (1998) (analyzing the conspiracy charges in light of ordinary criminal law principles at the time), is at best an equivocal exception. Although the charge against the defendants in that case accused them of “combining, confederating, and conspiring together” to murder the President, they were also charged (as we read the indictment, cf. post, at 23, n. 14 (Thomas, J., dissenting)) with “maliciously, unlawfully, and traitorously murdering the said Abraham Lincoln.” H. R. Doc. No. 314, 55th Cong., 1st Sess., 696 (1899). Moreover, the Attorney General who wrote the opinion defending the trial by military commission treated the charge as if it alleged the substantive offense of assassination. See 11Op. Atty. Gen. 297 (1865) (analyzing the propriety of trying by military commission “the offence of having assassinated the President”); see also Mudd v. Caldera, 134 F. Supp. 2d 138, 140 (DC 2001).

36 By contrast, the Geneva Conventions do extend liability for substantive war crimes to those who “orde[r]” their commission, see Third Geneva Convention, Art. 129, 6 U. S. T., at 3418, and this Court has read the Fourth Hague Convention of 1907 to impose “command responsibility” on military commanders for acts of their subordinates, see Yamshita, 327 U. S., at 15–16.

37 The other examples Justice Thomas offers are no more availing. The Civil War indictment against Robert Louden, cited post, at 25, alleged a conspiracy, but not one in violation of the law of war. See War Dept., General Court Martial Order No. 41, p. 20 (1864). A separate charge of “ ‘[t]ransgression of the laws and customs of war’ ” made no mention of conspiracy. Id., at 17. The charge against Lenger Grenfel and others for conspiring to release rebel prisoners held in Chicago only supports the observation, made in the text, that the Civil War tribunals often charged hybrid crimes mixing elements of crimes ordinarily triable in civilian courts (like treason) and violations of the law of war. Judge Advocate General Holt, in recommending that Grenfel’s death sentence be upheld (it was in fact commuted by Presidential decree, see H. R. Doc. No. 314, at 725), explained that the accused “united himself with traitors and malefactors for the overthrow of our Republic in the interest of slavery.” Id., at 689.

38 The Court in Quirin “assume[d] that there are acts regarded in other countries, or by some writers on international law, as offenses against the law of war which would not be triable by military tribunal here, either because they are not recognized by our courts as violations of the law of war or because they are of that class of offenses constitutionally triable only by a jury.” 317 U. S., at 29. We need not test the validity of that assumption here because the international sources only corroborate the domestic ones.

39 Accordingly, the Tribunal determined to “disregard the charges … that the defendants conspired to commit War Crimes and Crimes against Humanity.” 22 Trial of the Major War Criminals Before the International Military Tribunal 469 (1947); see also ibid. (“[T]he Charter does not define as a separate crime any conspiracy except the one to commit acts of aggressive war”).

40  See also 15 United Nations War Crimes Commissions, Law Reports of Trials of War Criminals 90–91 (1949) (observing that, although a few individuals were charged with conspiracy under European domestic criminal codes following World War II, “the United States Military Tribunals” established at that time did not “recognis[e] as a separate offence conspiracy to commit war crimes or crimes against humanity”). The International Criminal Tribunal for the former Yugoslavia (ICTY), drawing on the Nuremberg precedents, has adopted a “joint criminal enterprise” theory of liability, but that is a species of liability for the substantive offense (akin to aiding and abetting), not a crime on its own. See Prosecutor v. Tadi, Judgment, Case No. IT–94–1–A (ICTY App. Chamber, July 15, 1999); see also Prosecutor v. Milutinovi, Decision on Dragoljub Ojdani’s Motion Challenging Jurisdiction—Joint Criminal Enterprise, Case No. IT–99–37–AR72, ¶26 (ICTY App. Chamber, May 21, 2003) (stating that “[c]riminal liability pursuant to a joint criminal enterprise is not a liability for … conspiring to commit crimes”).

41 Justice Thomas’ suggestion that our conclusion precludes the Government from bringing to justice those who conspire to commit acts of terrorism is therefore wide of the mark. See post, at 8, n. 3; 28–30. That conspiracy is not a violation of the law of war triable by military commission does not mean the Government may not, for example, prosecute by court-martial or in federal court those caught “plotting terrorist atrocities like the bombing of the Khobar Towers.” Post, at 29.

42 The accused also may be excluded from the proceedings if he “engages in disruptive conduct.” §5(K).

43 As the District Court observed, this section apparently permits reception of testimony from a confidential informant in circumstances where “Hamdan will not be permitted to hear the testimony, see the witness’s face, or learn his name. If the government has information developed by interrogation of witnesses in Afghanistan or elsewhere, it can offer such evidence in transcript form, or even as summaries of transcripts.” 344 F. Supp. 2d 152, 168 (DC 2004).

44 Any decision of the commission is not “final” until the President renders it so. See Commission Order No. 1 §6(H)(6).

45 See Winthrop 835, and n. 81 (“military commissions are constituted and composed, and their proceedings are conducted, similarly to general courts-martial”); id., at 841–842; S. Rep. No. 130, 64th Cong., 1st Sess., 40 (1916) (testimony of Gen. Crowder) (“Both classes of courts have the same procedure”); see also, e.g., H. Coppée, Field Manual of Courts-Martial, p. 104 (1863) (“[Military] commissions are appointed by the same authorities as those which may order courts-martial. They are constituted in a manner similar to such courts, and their proceedings are conducted in exactly the same way, as to form, examination of witnesses, etc.”).

46 The dissenters’ views are summarized in the following passage: “It is outside our basic scheme to condemn men without giving reasonable opportunity for preparing defense; in capital or other serious crimes to convict on ‘official documents …; affidavits; … documents or translations thereof; diaries …, photographs, motion picture films, and … newspapers” or on hearsay, once, twice or thrice removed, more particularly when the documentary evidence or some of it is prepared ex parte by the prosecuting authority and includes not only opinion but conclusions of guilt. Nor in such cases do we deny the rights of confrontation of witnesses and cross-examination.” Yamashita, 327 U. S., at 44 (footnotes omitted).

47 Article 2 of the UCMJ now reads: “(a) The following persons are subject to [the UCMJ]: “(9) Prisoners of war in custody of the armed forces. “(12) Subject to any treaty or agreement to which the United States is or may be a party or to any accepted rule of international law, persons within an area leased by or otherwise reserved or acquired for the use of the United States which is under the control of the Secretary concerned and which is outside the United States and outside the Commonwealth of Puerto Rico, Guam, and the Virgin Islands.” 10 U. S. C. §802(a). Guantanamo Bay is such a leased area. See Rasul v. Bush, 542 U. S. 466, 471 (2004) .

48 The International Committee of the Red Cross is referred to by name in several provisions of the 1949 Geneva Conventions and is the body that drafted and published the official commentary to the Conventions. Though not binding law, the commentary is, as the parties recognize, relevant in interpreting the Conventions’ provisions.

49 Aside from Articles 21 and 36, discussed at length in the text, the other seven Articles that expressly reference military commissions are: (1) 28 (requiring appointment of reporters and interpreters); (2) 47 (making it a crime to refuse to appear or testify “before a court-martial, military commission, court of inquiry, or any other military court or board”); (3) 48 (allowing a “court-martial, provost court, or military commission” to punish a person for contempt); (4) 49(d) (permitting admission into evidence of a “duly authenticated deposition taken upon reasonable notice to the other parties” only if “admissible under the rules of evidence” and only if the witness is otherwise unavailable); (5) 50 (permitting admission into evidence of records of courts of inquiry “if otherwise admissible under the rules of evidence,” and if certain other requirements are met); (6) 104 (providing that a person accused of aiding the enemy may be sentenced to death or other punishment by military commission or court-martial); and (7) 106 (mandating the death penalty for spies convicted before military commission or court-martial).

50 Justice Thomas relies on the legislative history of the UCMJ to argue that Congress’ adoption of Article 36(b) in the wake of World War II was “motivated” solely by a desire for “uniformity across the separate branches of the armed services.” Post, at 35. But even if Congress was concerned with ensuring uniformity across service branches, that does not mean it did not also intend to codify the longstanding practice of procedural parity between courts-martial and other military tribunals. Indeed, the suggestion that Congress did not intend uniformity across tribunal types is belied by the textual proximity of subsection (a) (which requires that the rules governing criminal trials in federal district courts apply, absent the President’s determination of impracticability, to courts-martial, provost courts, and military commissions alike) and subsection (b) (which imposes the uniformity requirement).

51 We may assume that such a determination would be entitled to a measure of deference. For the reasons given by Justice Kennedy, see post, at 5 (opinion concurring in part), however, the level of deference accorded to a determination made under subsection (b) presum-ably would not be as high as that accorded to a determination under subsection (a).

52 Justice Thomas looks not to the President’s official Article 36(a) determination, but instead to press statements made by the Secretary of Defense and the Under Secretary of Defense for Policy. See post, at 36–38 (dissenting opinion). We have not heretofore, in evaluating the legality of Executive action, deferred to comments made by such officials to the media. Moreover, the only additional reason the comments provide—aside from the general danger posed by international terrorism—for departures from court-martial procedures is the need to protect classified information. As we explain in the text, and as Justice Kennedy elaborates in his separate opinion, the structural and procedural defects of Hamdan’s commission extend far beyond rules preventing access to classified information.

53 Justice Thomas relies extensively on Madsen for the proposition that the President has free rein to set the procedures that govern military commissions. See post, at 30, 31, 33, n. 16, 34, and 45. That reliance is misplaced. Not only did Madsen not involve a law-of-war military commission, but (1) the petitioner there did not challenge the procedures used to try her, (2) the UCMJ, with its new Article 36(b), did not become effective until May 31, 1951, after the petitioner’s trial, see 343 U. S., at 345, n. 6, and (3) the procedures used to try the petitioner actually afforded more protection than those used in courts-martial, see id., at 358–360; see also id., at 358 (“[T]he Military Government Courts for Germany . . . have had a less military character than that of courts-martial”).

54 Prior to the enactment of Article 36(b), it may well have been the case that a deviation from the rules governing courts-martial would not have rendered the military commission “ ‘illegal.’ ” Post, at 30–31, n. 16 (Thomas, J., dissenting) (quoting Winthrop 841). Article 36(b), however, imposes a statutory command that must be heeded.

55 Justice Thomas makes the different argument that Hamdan’s Geneva Convention challenge is not yet “ripe” because he has yet to be sentenced. See post, at 43–45. This is really just a species of the abstention argument we have already rejected. See Part III, supra. The text of the Geneva Conventions does not direct an accused to wait until sentence is imposed to challenge the legality of the tribunal that is to try him.

56 As explained in Part VI–C, supra, that is no longer true under the 1949 Conventions.

57 But see, e.g., 4 Int’l Comm. of Red Cross, Commentary: Geneva Convention Relative to the Protection of Civilian Persons in Time of War 21 (1958) (hereinafter GCIV Commentary) (the 1949 Geneva Conventions were written “first and foremost to protect individuals, and not to serve State interests”); GCIII Commentary 91 (“It was not … until the Conventions of 1949 … that the existence of ‘rights’ conferred in prisoners of war was affirmed”).

58 But see generally Brief for Louis Henkin et al. as Amici Curiae; 1 Int’l Comm. for the Red Cross, Commentary: Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field 84 (1952) (“It should be possible in States which are parties to the Convention … for the rules of the Convention to be evoked before an appropriate national court by the protected person who has suffered a violation”); GCII Commentary 92; GCIV Commentary 79.

59 For convenience’s sake, we use citations to the Third Geneva Convention only.

60 The President has stated that the conflict with the Taliban is a conflict to which the Geneva Conventions apply. See White House Memorandum, Humane Treatment of Taliban and al Qaeda Detainees 2(Feb. 7, 2002), available at http://www.justicescholars.org/pegc/archive/White_House/bush_memo_20020207_ed.pdf (hereinafter White House Memorandum).

61 Hamdan observes that Article 5 of the Third Geneva Convention requires that if there be “any doubt” whether he is entitled to prisoner-of-war protections, he must be afforded those protections until his status is determined by a “competent tribunal.” 6 U. S. T., at 3324. See also Headquarters Depts. of Army, Navy, Air Force, and Marine Corps, Army Regulation 190–8, Enemy Prisoners of War, Retained Personnel, Civilian Internees and Other Detainees (1997), App. 116. Because we hold that Hamdan may not, in any event, be tried by the military commission the President has convened pursuant to the November 13 Order and Commission Order No. 1, the question whether his potential status as a prisoner of war independently renders illegal his trial by military commission may be reserved.

62 The term “Party” here has the broadest possible meaning; a Party need neither be a signatory of the Convention nor “even represent a legal entity capable of undertaking international obligations.” GCIII Commentary 37.

63 See also GCIII Commentary 35 (Common Article 3 “has the merit of being simple and clear… . Its observance does not depend upon preliminary discussions on the nature of the conflict”); GCIV Commentary 51 (“[N]obody in enemy hands can be outside the law”); U. S. Army Judge Advocate General’s Legal Center and School, Dept. of the Army, Law of War Handbook 144 (2004) (Common Article 3 “serves as a ‘minimum yardstick of protection in all conflicts, not just internal armed conflicts’ ” (quoting Nicaragua v. United States, 1986 I. C. J. 14, ¶218, 25 I. L. M. 1023)); Prosecutor v. Tadi, Case No. IT–94–1, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction, ¶102 (ICTY App. Chamber, Oct. 2, 1995) (stating that “the character of the conflict is irrelevant” in deciding whether Common Article 3 applies).

64 The commentary’s assumption that the terms “properly constituted” and “regularly constituted” are interchangeable is beyond reproach; the French version of Article 66, which is equally authoritative, uses the term “régulirement constitués” in place of “properly constituted.”

65 Further evidence of this tribunal’s irregular constitution is the fact that its rules and procedures are subject to change midtrial, at the whim of the Executive. See Commission Order No. 1, §11 (providing that the Secretary of Defense may change the governing rules “from time to time”).

66 Other international instruments to which the United States is a signatory include the same basic protections set forth in Article 75. See, e.g., International Covenant on Civil and Political Rights, Art. 14, ¶3(d), Mar. 23, 1976, 999 U. N. T. S. 171 (setting forth the right of an accused “[t]o be tried in his presence, and to defend himself in person or through legal assistance of his own choosing”). Following World War II, several defendants were tried and convicted by military commission for violations of the law of war in their failure to afford captives fair trials before imposition and execution of sentence. In two such trials, the prosecutors argued that the defendants’ failure to apprise accused individuals of all evidence against them constituted violations of the law of war. See 5 U. N. War Crimes Commission 30 (trial of Sergeant-Major Shigeru Ohashi), 75 (trial of General Tanaka Hisakasu).

67 The Government offers no defense of these procedures other than to observe that the defendant may not be barred from access to evidence if such action would deprive him of a “full and fair trial.” Commission Order No. 1, §6(D)(5)(b). But the Government suggests no circumstances in which it would be “fair” to convict the accused based on evidence he has not seen or heard. Cf. Crawford v. Washington, 541 U. S. 36, 49 (2004) (“ ‘It is a rule of the common law, founded on natural justice, that no man shall be prejudiced by evidence which he had not the liberty to cross examine’ ” (quoting State v. Webb, 2 N. C. 103, 104 (Super. L. & Eq. 1794) (per curiam)); Diaz v. United States, 223 U. S. 442, 455 (1912) (describing the right to be present as “scarcely less important to the accused than the right of trial itself”); Lewis v. United States, 146 U. S. 370, 372 (1892) (exclusion of defendant from part of proceedings is “contrary to the dictates of humanity” (internal quotation marks omitted)); Joint Anti-Fascist Refugee Comm. v. McGrath, 341 U. S. 123 , n. 17, 171 (1951) (Frankfurter, J., concurring) (“[t]he plea that evidence of guilt must be secret is abhorrent to free men” (internal quotation marks omitted)). More fundamentally, the legality of a tribunal under Common Article 3 cannot be established by bare assurances that, whatever the character of the court or the procedures it follows, individual adjudicators will act fairly.