Customary international law (CIL) is under attack as behaviorally epiphenomenal and doctrinally incoherent. In this article, we reject both claims. To be sure, CIL is a feat of levitation; it rests not on a rock-solid natural law basis of divine principles, but on a fabric of rational acts, woven through a multiplicity of relations over time. And while there are limits on, and variations in, the effectiveness of CIL, we argue that there are circumstances where it may independently affect the behavior of states. There is no reason in theory, or in data adduced by others, to believe CIL to be generally epiphenomenal. Since certain components of CIL serve as the foundation of all international law, this article suggests the circumstances under which one would expect international law to affect state behavior.

International agreements exhibit a wide range of variation. Many are negotiated as legally binding agreements, while others are expressly nonbinding. Some contain substantive obligations requiring deep, demanding policy changes; others demand little or simply ratify the status quo ante. Some specify institutions to monitor and sanction noncompliance; others create no review structure at all. Thus, there is considerable variation both in the form of international agreements—in their legal bindingness, as well as in the range of structural provisions for monitoring and addressing noncompliance—and in the substantive obligations they impose. This variation in form and substance raises several fundamental questions about the role of international agreements in world politics.’ Why do states differentiate commitments into those which are legally binding and those which are not? What relationship exists between legality and the substantive provisions of an accord, and between legality and structural provisions for monitoring behavior? What is the relationship between substantive obligations and monitoring provisions? Finally, what difference, if any, do these choices make as to the effectiveness of an agreement?

In its decision on assigned counsel's motion for withdrawal in the Milosevic case, the trial chamber of the International Criminal Tribunal for the Former Yugoslavia (ICTY) observed “that assignment of counsel against the wishes of the accused is a developing area of the law both in national and international jurisdictions.” This area of law witnessed rapid development by international criminal tribunals in the latter half of 2004.