Perhaps because of the functionalist orientation of the seminal texts on legalization in international relations (Abbott, Keohane, Moravcsik, Slaughter, & Snidal, 2000), it is generally assumed that the causal arrow between states and law is unidirectional. That is, it is commonly assumed that states make law, and that is that. However, it seems just as plausible that international society, as a society, is constituted by its norms, which entails that states, to the extent they maintain this status by virtue of being members in international society, are also constituted by the process of legalization. In effect, states make laws, and laws make states. This paper will propose a reversal of the causal arrow by comparing the historical development of two spontaneous international conventions: the three-mile rule of territorial seas and the most-favoured-nation principle of international trade law. As a concept, spontaneous international conventions are rules of international society whose form is arbitrary relative to their function and that are not the result of explicit negotiation, much like rules of etiquette or grammar. Both of the cases chosen could serve their ostensible functions as well – or better – under alternative formulations, and both have been formulated in different ways over the last five centuries, until they were both codified and multilateralized relatively recently. This element of arbitrariness suggests a remarkable degree of contingency, leading to the question: if multiple formulations are equally functional, bilateral arrangements served the purpose as well as multilateral ones, and they even worked without centralized codification, why have they been codified and multilateralized at all? The answer, I suggest, is because these regulative norms also serve to constitute international society, and by extension, states themselves. Taken a step further, this also enables the hypothesis from a more critical perspective that this might not merely be a side effect of legalizing spontaneous conventions; it might be the whole point.
