Searching for State Practice

I’m wondering whether customary international law really exists anymore. No, I’m not talking about Posner and Goldsmith’s use of rational choice methodology to attack the normative value of customary international law; I’m not looking to quarrel with this blog’s namesake, opinio juris, or its effects on relations between states and other subjects of international law. Rather, my inquiry stems from how we conceive of custom’s creation. Traditionally, customary international law was defined as (1) a state practice of (2) some generality among states, with (3) sufficient uniformity in the practice itself, that (4) states perform out of a sense of legal obligation (a.k.a. the aforementioned opinio juris). Debates over customary international law have long focused on the last three elements – i.e., does customary international law regulate a state that has persistently or subsequently objected to the practice? What happens to custom when a state’s practice deviates from the existing rule? How do we tell when a practice derives from a sense of legal obligation as opposed to political expediency (or, to use the modern parlance, national interest)?

I think these are all important questions and ones we’ll likely see subject to continuing debate. They all hinge, however, on the idea that it is the practice of states that creates customary international law. But is state practice still the driving force for defining what constitutes customary international law? In reality, isn’t most of what we regard as custom today derived not from what states do, but what states have generally agreed they should do. Aren’t treaties now the default source for finding a customary international law binding on states who are not bound by the treaty itself? For example, when faced with a question of diplomatic law, do you actually survey state practice to decide what’s the current state of customary diplomatic law? I don’t think so. Rather, I expect most international lawyers turn to the Vienna Convention on Diplomatic Relations as a “codification” of the customary rules (even if at the time of its formulation some of its terms were not entirely consistent with state practice). And wouldn’t you use treaties in a similar fashion to identify other key areas of customary international law — e.g., the law of treaties, the laws of war, or the law of the sea?

This leads me to three questions. First, is my premise correct that most custom today is delineated in written instruments rather than the observed practice of states? Are there any areas where custom remains the product of state action (or inaction) in lieu of negotiated texts reflecting states’ visions of what the law is (or should be)? I’d be interested in specific examples if readers have any to offer. Second, is the simple solution to this change to widen our conception of what constitutes “state practice” to incorporate the act of negotiating or agreeing to certain principles, even in the absence of states’ actual observance of those principles? Or, does the fact that states don’t necessarily practice what they preach undermine the whole conception of customary international law? Finally, if you accept my proposition that we are no longer identifying custom through state practice, what implications, if any, does this have for it as a source of international law? Should we be rethinking the whole notion of custom or, for that matter, treaties? For example, couldn’t we divide a treaty’s legal force depending upon whether it has received a state’s specific consent (consistent with the age-old conception of pacta sunt servanda), while at the same time recognizing that treaties can still bind non-consenting states if the treaty otherwise has sufficient support from the international community as a whole (which seems to actually be the case with so many general “law-making” treaties today)? I know I’m not the first to wrestle with these issues, so I’m interested to hear how others would address these questions.