Opinion of Gorsuch, J.
customary international law as federal law when it enumerates sources of “the supreme Law of the Land.” And Article I vests Congress rather than the Judiciary with the power to “define and punish … Offences against the Law of Nations.” §8, cl. 10. See Sosa v. Alvarez-Machain, 542 U. S. 692, 739–742 (2004) (Scalia, J., concurring in part and concurring in judgment); Jesner v. Arab Bank, PLC, 584 U. S. ___, ___–___ (2018) (Gorsuch, J., concurring in part and concurring in judgment) (slip op., at 4–5); Nestlé USA, Inc. v. Doe, 593 U. S. ___, ___ (2021) (Gorsuch, J., concurring) (slip op., at 3).
Perhaps Article III incorporated customary international law into federal common law. But since Erie R. Co. v. Tompkins, 304 U. S. 64 (1938), federal courts have largely disclaimed the power to develop federal common law outside of a few reserved areas. See Sosa, 542 U. S., at 740–742 (opinion of Scalia, J.). And whether customary international law survives as a form of federal common law after Erie is a matter of considerable debate among scholars. Compare C. Bradley & J. Goldsmith, Customary International Law as Federal Common Law: A Critique of the Modern Position, 110 Harv. L. Rev. 815 (1997), with H. Koh, Is International Law Really State Law?, 111 Harv. L. Rev. 1824 (1998). Must lower courts confront this long-running debate to resolve a claim of foreign sovereign immunity in criminal cases? And if there is no federal law at work here that might apply under the Supremacy Clause, only general common-law principles, what constraints remain on state prosecutions of foreign sovereigns? * Today’s decision overcomplicates the law for no good reason. In the FSIA, Congress supplied us with simple rules for resolving this case and others like it. Respectfully, I would follow those straightforward directions to the same straightforward conclusion the Second Circuit reached: This case against Halkbank may proceed.
