The federal common law of foreign relations has been in decline for decades. The field was built in part on the claim that customary international law is federal common law and in part on the claim that federal judges should displace state law when they conclude that it poses difficulties for U.S. foreign relations. Today, however, customary international law is generally applied based upon the implied intentions of Congress, rather than its free-standing status as federal common law, and judicial evaluation of foreign policy problems has largely been replaced by reliance upon presidential or congressional action, or by standard constitutional analysis. Two traditional areas of the federal common law of foreign relations–immunity and the act of state doctrine–are alive and well doctrinally. Their status as federal common law is somewhat unsteady, however, because the Court has not provided a convincing account of why these two topics should be governed by federal common law, and because the traditional basis for the federal common law of foreign relations have eroded. In an important new book, The Law of Nations and the United States Constitution, Anthony J. Bellia, Jr. and Bradford R. Clark argue that the Constitution itself requires courts to apply customary international law in these two areas. Their argument fails to convince. A better alternative is to justify federal common law as necessary to give effect to the very closely-related statutory framework governing foreign sovereign immunity, and because judicial lawmaking is also cabined by the content of customary international law and by some actions of the executive branch. The federal common law of foreign relations does have a future, but it depends neither upon the status of customary international law as federal common law nor upon judicial decision-making about the deleterious effect of state law upon U.S. foreign policy.