The Death of a Customary Rule of International Law
Like Duncan, I had my first week of public international law. In a brief introductory discussion on customary international law one of the students asked, “How does a practice that has achieved the status of customary international law cease to become customary international law?” It is an interesting question. We spend plenty of time in international law classes discussing the formation of customary international law, but rarely do we examine the death of a custom.
Obviously there are a number of possible answers. A custom may be superseded by a treaty. Likewise, subsequent state practice may conflict with a previous norm, such that the emergence of one norm results in the eclipse of another. But the question also raises the possibility that customary international law may cease to exist under the doctrine of desuetude. It seems quite possible that some customs can become obsolete, but I struggle to think of many examples.
A quick search reveals that the question of applying the doctrine of desuetude to customary international law has rarely been examined by international law scholars. In this article, Michael Glennon has written a little about the doctrine, including the following provocative statement:
The idea of a tipping point, for example, is hardly unique to the notion of desuetude. It is a core problem in the methodology of customary international law formation, which requires the same inquiry in determining the point at which a nascent or emerging customary norm becomes binding. Traditional international law doctrine provides little useful guidance in telling us when that has happened. The emergence of desuetude with respect to a dying norm is no different. At some point, the balance tips; at some point, the rule changes; at some point, obligation shifts. Whether the issue is a rule’s birth or death, the process is the same.
I query whether that is accurate. Customary rules die in the same way they are formed, by reaching a certain tipping point in which they are no longer binding? That would seem to suggest that customary international law can only die when a practice no longer remains general and consistent. On this logic, a rule ignored by the majority of states ceases to be a rule altogether. Or does it remain binding for those minority states that continue with the practice? Is it also possible that a practice remains general and consistent, but that it ceases to be binding because opinio juris falls away? “We used to do it because we felt we had to, but now we don’t think we have to do it, we just do it because we want to do it.” Is that enough?
Just to give you a concrete example, I was at a conference at Stanford a few years ago with a bunch of international tribunal judges. Very impressive crowd. In the context of discussing pacta sunt servanda I made the passing comment that in the WTO context it appears patently clear that almost every prominent state is engaging in “efficient breach” behavior, making certain policy choices not to comply with WTO panel decisions and pay the consequences (including monetary penalties in the form of sanctioned tariff increases). Not surprisingly, I received a vigorous challenge from one of the most eminent judges in the world (who, by the way, was not a WTO expert). But the judge never answered the question as applied to the specific context in which I raised it. Is it possible that the doctrine of pacta sunt servanda (which of course is both a VCLT treaty obligation and a customary norm) is no longer followed at least in certain contexts? And if so, what does that say about the norm?