Article I, Section 8, Clause 18:

[The Congress shall have Power . . . ] To make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers, and all other Powers vested by this Constitution in the Government of the United States, or in any Department or Officer thereof.

Congress’s power to conduct investigations stands on equal footing with its authority to legislate and appropriate.1 Although the “power of inquiry” was not expressly provided for in the Constitution, it has nonetheless been acknowledged as “an essential and appropriate auxiliary to the legislative function” derived implicitly from Article I’s vesting of “legislative Powers” in the Congress.2 This implied constitutional prerogative to gather information related to legislative activity is both critical in purpose, as Congress “cannot legislate wisely or effectively in the absence of information,” and extensive in scope, as Congress is empowered to obtain pertinent testimony and documents through investigations into nearly any matter.3 Included within the scope of the power is the authority to initiate investigations, hold hearings, gather testimony or documents from witnesses, and, in situations where either a government or private party is not forthcoming, compel compliance with congressional requests through the issuance and enforcement of subpoenas.

While Congress’s investigative tools can be used to achieve a number of different purposes, congressional practice suggests that legislative inquiries primarily serve to either gather information valuable for considering and producing legislation (what may be called the self-informing or legislative-informing function)4 or to ensure that existing laws are being properly administered (what may be referred to as the oversight function.)5 Although functionally distinguishable, the self-informing and oversight functions often merge during the conduct of significant investigations.

In the absence of explicit constitutional text, the scope of the investigatory power has been molded and defined primarily by congressional practice, negotiations between the political branches, and opinions of the Supreme Court. The Supreme Court has only rarely engaged in any significant discussion of Congress’s investigatory power, and in fact has only once issued an opinion directly addressing an investigative oversight conflict between Congress and the Executive Branch.6 A variety of factors contribute to the reduced judicial role in this area, including legal principles of judicial restraint and the separation of powers. But at least historically, the chief constraint appears to be the infrequency in which cases involving the investigatory power have been adjudicated.7 As a general matter, the Judicial Branch generally has become involved in subpoena disputes in only three classes of cases: (1) when a party is subject to a contempt proceeding for failure to comply with congressional demands;8 (2) when the House or Senate itself initiates a lawsuit in an attempt to enforce a subpoena—though the Supreme Court has never heard such a case;9 or (3) when a subpoena seeks an individual’s documents from a third party, and the individual brings suit to block the third party from complying with the subpoena.10 The majority of cases have historically come from the first category, arising either in the context of a criminal prosecution for contempt of Congress, or a habeas proceeding stemming from a detention carried out pursuant to an exercise of Congress’s inherent contempt power.11 The relative dearth of jurisprudence means that historical practice, especially Congress’s views of the reach of its own authority established through hundreds of years of investigations, plays a substantial role in establishing the outer bounds of the investigatory power.

Although Supreme Court decisions in this area are limited, they illuminate the basic constitutional foundation of Congress’s investigatory power and establish key legal limitations on its exercise. The Court’s early jurisprudence began with a focus on establishing the source of the investigatory power before considering the power’s scope.12 In that vein, the Court established that the authority to conduct investigations was implied from the “legislative power” vested in Congress by Article I of the Constitution, but only to the extent that an inquiry actually served a “legislative purpose.” 13 By the mid-twentieth century, judicial recognition of the investigatory power had been well established, and the Court’s focus shifted to legal limitations on congressional inquiries, generally in the context of the tension between congressional investigations and the individual rights of private citizens.14 These judicially identified limitations on Congress’s power of inquiry emanated principally from the Bill of Rights, including the First and Fifth Amendments, as well as from the internal rules of the House and Senate, which can act as self-imposed constraints on the investigatory power. Intervention by the Supreme Court into investigative disputes has generally been confined to scenarios in which Congress is seeking information from a private citizen, rather than a government official. Trump v. Mazars, decided in 2020, was the first time the Supreme Court directly addressed an interbranch investigatory conflict. Even then, the case was technically brought by President Donald Trump in his private rather than official capacity, though the Court chose to treat the conflict as one between the branches.15 Instead, the historical reality has generally been that inter-branch investigative conflicts are resolved through an informal tug-of-war between the political branches rather than through adjudication by the courts.16

Footnotes

1

Barenblatt v. United States, 360 U.S. 109, 111 (1959); Woodrow Wilson, Congressional Government 303 (15th ed. 1913) (asserting that the “informing function of Congress should be preferred even to its legislative function” ). See also J. William Fulbright, Congressional Investigations: Significance for the Legislative Process, 18 U. Chi. L. Rev. 440, 441 (1951) (describing the power of investigation as “perhaps the most necessary of all the powers underlying the legislative function” ).

2

See McGrain v. Daugherty, 273 U.S. 135, 174 (1927) ( “We are of opinion that the power of inquiry—with process to enforce it—is an essential and appropriate auxiliary to the legislative function.” ).

3

Id. at 175 ( “A legislative body cannot legislate wisely or effectively in the absence of information respecting the conditions which the legislation is intended to affect or change; and where the legislative body does not itself possess the requisite information—which not infrequently is true—recourse must be had to others who do possess it.” ). Congress’s oversight function is subject to a variety of legal limitations. See Eastland v. United States Servicemen’s Fund, 421 U.S. 491, 504 n.15 (1975) ( “Although the power to investigate is necessarily broad it is not unlimited . . . . We have made it clear [ ] that Congress is not invested with a ''general’ power to inquire into private affairs.’ The subject of any inquiry always must be one ‘on which legislation could be had.’” ) (citations omitted). For a discussion of other constitutional limitations on congressional investigations see CRS Report RL30240, Congressional Oversight Manual, by Christopher M. Davis et al.

4

Congressional investigations have previously served to either inform Congress itself (for purposes of a legislative function) or to inform the public. See Hutchinson v. Proxmire, 443 U.S. 111, 132 (1979) ( “Advocates of a broad reading of the “informing function” sometimes tend to confuse two uses of the term ‘informing.’ In one sense, Congress informs itself collectively by way of hearings of its committees . . . . The other sense of the term . . . perceives it to be the duty of Members to tell the public about their activities.” ). While the self-informing function is clearly a valid justification for exercise of the investigative power, the public-informing function sits on less certain ground. Id. ( “Valuable and desirable as it may be in broad terms, the transmittal of such information by individual Members in order to inform the public and other Members is not a part of the legislative function or the deliberations that make up the legislative process.” ) But see Watkins v. United States, 354 U.S. 178, 200 n.33 (1957) (noting that “[f]rom the earliest times in its history, the Congress has assiduously performed an ‘informing function’” the purpose of which is to “inquire into and publicize corruption, maladministration or inefficiency in agencies of the Government” ) (emphasis added).

5

Watkins v. United States, 354 U.S. 178, 187 (1957) (holding that the investigatory power “encompasses inquiries concerning the administration of existing laws” ).

6

Prior to Trump v. Mazars, 140 S. Ct. 2019 (2020), the Court’s last significant discussion of the scope of the investigatory power was in 1975. Eastland, 421 U.S. at 505–11.

7

See Rumely, 345 U.S. at 46–48 ( “Experience admonishes us to tread warily in this domain . . . . Grave constitutional questions are matters properly to be decided by this Court but only when they inescapably come before us for adjudication. Until then it is our duty to abstain from marking the boundaries of congressional power . . . . Only by such self-restraint will we avoid the mischief which has followed occasional departures from the principles which we profess.” ). The Court has limited a witness’s options for challenging a subpoena. For example, in Eastland, the Court held that the Speech or Debate Clause severely limits a court’s ability to quash a congressional subpoena in a civil case. See Eastland, 421 U.S. at 511 (forbidding “invocation of judicial power to challenge the wisdom of Congress’s use of its investigative authority” ).

8

See, e.g., Watkins, 354 U.S. at 181–82.

9

See, e.g., Comm. on the Judiciary of the United States House of Representatives v. McGahn, 968 F.3d 755, 762 (D.C. Cir. 2020) (House lawsuit to enforce a committee subpoena).

10

See, e.g., Mazars, 140 S. Ct. at 2028.

11

Trump v. Mazars and Eastland v. United States Serviceman’s Fund represent two opinions that come from outside the contempt context. Mazars, 140 S. Ct. at 2028–29 (involving a lawsuit filed by President Donald Trump to block his accounting firm from complying with a congressional subpoena); Eastland, 421 U.S. at 493–501 (involving application of the Speech or Debate Clause in a challenge to a congressional subpoena).

12

See Watkins, 354 U.S. at 195 ( “Prior cases . . . had defined the scope of investigative power in terms of the inherent limitations of the sources of that power. In the more recent cases, the emphasis shifted to problems of accommodating the interest of the Government with the rights and privileges of individuals.” ).

13

Kilbourn v. Thompson, 103 U.S. 168, 204 (1880) (holding that exercise of Congress’s implied power of inquiry must be made “in aid of the legislative function” ).

14

See e.g., Watkins, 354 U.S. at 215 ( Fifth Amendment Due Process); Quinn v. United States, 349 U.S. 155, 161–65 (1955) ( Fifth Amendment privilege against self-incrimination); Barenblatt, 360 U.S. at 125–34 ( First Amendment).

15

Mazars, 140 S. Ct. at 2028, 2034 ( “The interbranch conflict here does not vanish simply because the subpoenas seek personal papers or because the President sued in his personal capacity.” ).

16

Andrew McCanse Wright, Constitutional Conflict and Congressional Oversight, 98 Marq. L. Rev. 881, 889–90 (2014) (arguing that “the constitutional scheme places a premium on good faith negotiation between Congress and the Executive backstopped by rare instances of judicial resolution . . . . In cases of impasse, Congress primarily enforces its requests through political self-help remedies rather than outsourcing enforcement to the courts. When Congress does seek judicial enforcement, restraint is generally the hallmark of Article III tribunals presented with bickering political branches.” ).