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Pursuant to Article II of the Constitution, the President has the power to make treaties with the advice and consent of two-thirds of the Senate, and these treaties uncontroversially become binding on the United States as a matter of international law. The status of such treaties within the U.S. legal system is less clear. The Supremacy Clause states that, along with the Constitution and laws of the United States, treaties made by the United States are part of the"supreme Law of the Land." At least since the Supreme Court's 1829 decision in Foster v Neilson, however, it has been understood that treaty provisions are directly enforceable in U.S. courts only if they are "self-executing."1 The legitimacy and implications of this self-execution requirement have generated substantial controversy and confusion among both courts and commentators.

Much of the debate over self-execution has been fought out, at least in part, on originalist territory, with competing claims about what the constitutional Founders would have understood. Whatever one may think of the virtues of originalist methodology in general, it has not been successful in moving the self-execution debate forward. Among other things, both treaty practice and the nation's position in the world have changed so dramatically since the Founding that is difficult for originalism to compel contemporary conclusions. It is noteworthy, for example, that most scholarship on self-execution hardly mentions the phenomenon of congressional-executive agreements (which are ratified by the President with the approval of a majority of both houses of Congress rather than two-thirds of the Senate), even though they constitute the vast majority of international agreements concluded by the United States since the 1930s.2 Similarly, the development in the modern era of legislative-style multilateral treaties, many of which overlap substantially with domestic legislation, poses issues not contemplated by the Founders.3

The Supreme Court's decision last Term in Medellin v Texas contains the most extensive discussion of treaty self-execution in the Court's history.4 In that case, the Court held that a treaty obligation of the United States to comply with a decision of the International Court of Justice (the international adjudicatory arm of the United Nations that sits in The Hague) was not self-executing and thus could not be applied by U.S. courts to override an otherwise valid state rule of criminal procedure. The Court also held that the President lacked the unilateral authority to compel state courts to comply with the International Court's decision. The decision is both controversial and subject to differing interpretations and thus, if anything, is likely to intensify the debate.

My goal in this article is to clear up some conceptual confusion relating to the self-execution doctrine and, in the process, better explain the contemporary practice of the courts and politicalbranches relating to treaty enforcement. To that end, I will make three claims about treaty self-execution. First, the Supremacy Clause does not by itself tell us the extent to which treaties should be judicially enforceable. Second, the relevant intent in discerning self-execution is the intent of the U.S. treaty-makers (that is, the President and Senate), not the collective intent of the various parties to the treaty. Third, even if treaties and statutes have an equivalent status in the U.S. legal system in the abstract, there are important structural and functional differences between them that are relevant to judicial enforceability.

As will be shown, these three claims are interconnected. The central theme connecting them is that treaties have a dual nature,in that they operate both within the domain of international politics as well as within the domain of law. In addition to having a certain status within international law, and potentially also within domestic law, every treaty is a contract that implicates the U.S. relationship with one or more other nations, and such a relationship inherently includes political as well as legal elements, such as considerations of reciprocity, reputation, and national interest. This duality of treaties is in turn relevant, as I will explain, to their domestic judicial enforceability.5 The three claims set forth in this article are also complementary, in that each of them is best understood along with the other two, and together they present a relatively coherent explanation for the judicial precedent in the area, including (despite its ambiguities) the Medellin decision, as well as the practices of the political branches.

Part I of this article briefly reviews the academic debates over treaty self-execution, some of the uncertainties surrounding the issue, and what is at stake. Part II defends and explains the implications of my first claim: that the Supremacy Clause does not by itself tell us the extent to which treaties should be judicially enforceable. Part III defends the second claim: that the relevant intent concerning self-execution is that of the U.S. treaty-makers. Part IV defends the third claim: that, even if statutes and treaties have equivalent legal status in the abstract, they are different in important ways that relate to judicial enforceability. Finally, Part V explains how Medellin, despite its ambiguities, is generally consistent with these three claims.

In staking out these claims, I will refer extensively to the work of Professor Carlos Vázquez, who has been the most prolific and sophisticated theorist about treaty self-execution and who recently published an important article on the topic in the Harvard Law Review. Although my article will focus primarily on points of disagreement between us, I should emphasize at the outset that there are many points relating to treaty self-execution on which we agree, and I have benefited greatly from his work on the subject.

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