“Presidents have come to dominate the making, interpretation, and termination of international law for the United States. Often without specific congressional concurrence, and sometimes even when it is likely that Congress would disagree, Presidents assert the authority to (a) make a vast array of international obligations for the United States, through both written agreements and the development of customary international law; (b) make increasingly consequential political commitments for the United States on practically any topic; (c) interpret these obligations and commitments; and (d) terminate or withdraw from these obligations and commitments. While others have examined pieces of this picture, no one has considered the picture as a whole. For this and other reasons, commentators have failed to appreciate the overall extent of presidential unilateralism in this area, as well as the extent to which Presidents are able to shift between different pathways of authority in order to circumvent potential restraints. This trend, moreover, has become more pronounced in recent years. In many ways, the growth of this vast executive control over international law resembles the rise of presidential power in other modern contexts ranging from administrative law to covert action. Unlike in those other contexts, however, there is no systematic regulatory apparatus to guide or review the exercise of presidential control over international law. After presenting a descriptive account of the rise of such control, the Article turns to normative issues about the legality and broader legitimacy of this practice. It concludes that much of the modern practice has a plausible legal foundation but that some recent presidential actions and arguments relating to international agreements are questionable under generally accepted separation of powers principles. It also explains that the broader legitimacy question is difficult to assess because it turns on contested issues about the aims of presidential control, its efficacy in practice, and the costs and benefits of possible accountability mechanisms. After mapping out these and related considerations, the Article argues for one general accountability reform: significantly heightened transparency of executive branch actions and their legal bases. The Article then assesses the costs and benefits of additional accountability reforms that might become appropriate as more information about presidential control comes to light.”