The distinction between self-executing and non-self-executing treaties first emerged in the early 19th Century in the United States, where it has thoroughly confounded the courts. Since then, the distinction has been adopted by the courts of other countries. At a general level, a self-executing treaty is one that may be directly applied in the courts, whereas a non-self-executing treaty is one that requires legislative implementation before it may be applied by the courts (and other domestic law-applying officials). Among the many disputed aspects of this doctrine is whether a treaty's self-executing character is purely a matter of municipal law, or is also addressed by international law. Most scholars in the United States regard a treaty's self-executing character as solely a matter of domestic law -- a view that has recently been embraced in the Fourth Restatement of Foreign Relations Law. This view finds support in the fact that, under the constitutional law of some states (for example, the United Kingdom), treaties as a rule may not be enforced by the courts except via implementing legislation, yet many treaties to such dualist states are parties have been found by the U.S. courts to be self-executing. Non-US scholars, on the other hand, have taken the position that a treaty's self-executing character is a matter of international law. This position finds some support in statements by international adjudicatory (and quasi-adjudicatory) bodies that certain treaties are self-executing and others are non-self-executing.
This presentation will examine the distinction between self-executing and non-self-executing treaties from the perspective of international law. There is of course nothing in international law that prevents the parties to a treaty from agreeing that the treaty must be directly applied by the courts (and other law-applying officials) without intervening acts of legislation. But dualist states would not be able to join such treaties without amending their constitutions, and some treaties to which such states have become parties are regarded as self-executing by monist states. The parties to a treaty could also, in theory, decide to prohibit the domestic enforcement of a treaty in the absence of implementing legislation. But it seems unlikely that the parties to a treaty would want to prohibit direct enforcement of the treaty by states that wish to do so. In any event, treaties have been described as "non-self-executing" even though they cannot plausibly be read to prohibit direct judicial enforcement. The term "non-self-executing" might instead refer to a treaty that permits the parties to disable their courts from enforcing the treaty in the absence of implementing legislation, but, for reasons already noted, all treaties (or at least all multilateral treaties to which dualist states are parties) implicitly permit such indirect enforcement. What exactly is meant by the statement that a treaty is self-executing or non-self-executing as a matter of international law thus presents an intriguing puzzle.
Carlos M. Vázquez, Professor of Law at the Georgetown University Law Center in Washington, D.C., is currently the director of the Center for Transnational Legal Studies in London. He writes and teaches in the areas of Public International Law, Conflict of Laws, Foreign Relations Law, and U.S. Constitutional Law. He was a member of the U.N. Committee for the Elimination of Racial Discrimination from 2012 to 2016, and of the Inter-American Juridical Committee from 2000 to 2003. He is a member of the American Law Institute, where he is an adviser to the Fourth Restatement of Foreign Relations Law and a member of the Members' Consultative Group for the Third Restatement of Conflict of Laws. He was a member of the Board of Editors of the American Journal of International Law from 2007 to 2017. His writing on the distinction between self-executing and non-self-executing treaties received the Francis Déak Prize from the American Society of International Law and has been cited in U.S. Supreme Court opinions.