Over its constitutional history, the United States has developed multiple ways of joining, implementing, and terminating treaties and other international commitments. This chapter provides an overview of the law governing these pathways and considers the extent to which comparative law has influenced them or could do so in the future. Focusing in particular on the making of international commitments, the chapter describes how, over time, the United States came to develop alternatives to the process set out in the U.S. Constitution’s Treaty Clause, which requires the approval of two-thirds of the Senate. These alternatives arose partly from reasons of administrative efficiency and partly from presidential interest in making important international commitments in situations where two-thirds of the Senate would be unobtainable. These alternatives have had the effect of considerably increasing the president’s constitutional power to make international commitments. Nonetheless, considerable constraints remain on presidential power in this context, with some of these constraints stemming from constitutional law and others from statutory, administrative, and international law. With respect to comparative law, the chapter observes that U.S. practice historically has been largely but not entirely self-contained. Looking ahead, comparative practice is unlikely to affect U.S. constitutional law with respect to international agreements, but it might hold insights for legislative or administrative reforms.