The Alien Tort Statute ("ATS"; also known as the Alien Tort Claims Act) refers to 28 U.S.C. § 1350, granting jurisdiction to federal district courts "of all causes where an alien sues for a tort only in violation of the law of nation or of a treaty of the United States." Broadly speaking, it serves as a statutory instrument for gaining universal jurisdiction over violations of international law.
A lawsuit under the ATS can proceed for any harm resulting from a violation of international law, no matter where the harm occurred, or who inflicted the harm, as long as the plaintiff serves process in U.S. Territory. Filártiga v. Peña-Irala, 630 F.2d 876 (2d Cir. 1980). ATS claims can proceed against both natural persons and legal persons, but claims against state governments are precluded by sovereign immunity. Sosa v. Alvarez-Machain, 542 U.S. 692 (2004).
According to Law Professor George Fletcher, “the kind of torts that qualify as violations of the law of nations are widely condemned, egregious acts of wrongdoing.” The international legal norms that will qualify as a cause of action under ATS must be “specific, universal, and obligatory.” Sosa at 732. For example, it has been held that genocide, war crimes, and crimes against humanity (and torture contributing to these crimes) are paradigmatic violations of the law of nations under ATS, even when committed by an individual divorced from state action. Kadic v. Karadzic, 70 F.3d 232 (2d Cir.1995). Far less egregious acts have been found to be litigable violations under ATS, however. In Adra v. Clift, 195 F.Supp. 857 (D.Md.1961), a federal district court in Maryland found that passport fraud was litigable under ATS. On the other hand, the Supreme Court in Sosa held that a brief unlawful detention in which torture occurred did not warrant ATS damages.