Customary International Law and Withdrawal Rights in an Age of Treaties

Abstract

The conventional wisdom among international law scholars is that, once a rule of customary international law (CIL) becomes established, nations never have the unilateral right to withdraw from it. In a recent article published in the Yale Law Journal, Withdrawing from International Custom, we termed this conventional wisdom the Mandatory View of CIL and distinguished it from a possible regime in which nations could opt out of at least some CIL rules through advance notice, something we termed a Default View of CIL. After considering the intellectual origins and functional desirability of the Mandatory View, as well as the extent to which withdrawal rights are available under treaties, we concluded that it was difficult to justify a complete ban on withdrawal from all rules of CIL. That article is the subject of a forthcoming symposium edition of the Duke Journal of Comparative and International Law, in which a variety of scholars raise important questions about our analysis and its implications. In this essay, we seek to advance the analysis set forth in Withdrawing by addressing four topics implicated by the symposium responses: the current state of CIL; the proper way to conceive of CIL and its relationship to treaties; how a shift away from the Mandatory View might occur in practice; and whether a shift to a Default View would make a meaningful difference in state practice. We also identify some issues that could benefit from additional research