Treaties, Custom, Iteration, and Public Choice

The basic question asked in this paper can be simply stated. Assume that, in attempting to effect international legal cooperation, a national government consciously chooses between using treaties and using customary law as the form in which to embody its cooperative efforts. Which form of international law should we expect it to choose? I analyze this question using two approaches that may be termed "rational choice" methodologies since they assume that the relevant decisionmakers rationally pursue known goals.1 The first approach, which I call the "iterative perspective," focuses on the efforts of a rational, public-minded government to minimize the transaction costs of international cooperation.2 The iterative perspective implies that nation-states will choose to effect international legal cooperation through treaties.3 The second approach, which I call the "public choice" approach,4 examines the choices of self-interested governmental subunits." The public choice perspective predicts that national leaders will choose customary international law to effect international legal cooperation. With these divergent theoretical predictions in mind, I move to reality and argue that treaties rather than customary laws have been the favored embodiment of international legal cooperation, at least since World War II. I conclude that the evidence is thus more consistent with the iterative perspective than with the public choice approach. I. TREATIES, CUSTOM, AND THE ITERATIVE PERSPECTIVE A. TREATIES AND THE ITERATIVE PERSPECTIVE Treaty and custom are generally identified as the most prominent sources of international law.6 In previous work,7 I have argued that the law of treaties-the set of general procedural rules governing the degree of obligation imposed upon nations by the text of any particular treaty8-is consistent with an institutional design aimed at promoting a formally delineated series of structured interactions among parties ("iterations"), and that such an institutional design fosters cooperative behavior against the backdrop of the Prisoner's Dilemma typically thought to confront nation-states considering international political cooperation.9 In a complex world offering broad gains from cooperation but significant incentives to cheat, nations should structure their interactions to facilitate gradual cooperation over a number of clearly defined iterations, delineating what behavior constitutes cooperation at each interval. The law of treaties specifies a set of rules for the promulgation of international agreements that results in a highly structured and iterative process with three distinct phases. First, potential parties to a treaty, guided by a relatively vague duty to act in good faith, meet in formalized international negotiations. second, after these negotiations conclude, representatives from the participating nations decide either to reject the resulting text or to adopt it through an affirmative vote or signature.10 Adoption here functions differently from signature in the typical domestic contract, particularly because of its inability to upgrade a negotiated text into a fully binding legal instrument.11 Adopting nations must usually only refrain from actions that would undermine the object or purpose of the preliminary text. The third phase of the treaty process begins when a treaty enters into force, an event ordinarily occurring within a given time after a specified number of nations have gone beyond mere adoption to indicate formally their complete consent to the treaty. Both the threshold number of fully consenting nations-who "ratify" the treaty (if they have previously adopted its text) or "accede to" the treaty (if they have not)'2-and the requisite interval between the triggering ratification and the initial entry into force are typically elucidated by the relevant treaty. In contrast to the limited obligations flowing from adoption, a party that has ratified a treaty in force is bound to comply fully with all of that treaty's terms. …