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. 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. The iterative perspective implies that nation-states will choose to effect international legal cooperation through treaties. The second approach, which I call the public choice approach, 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