The emergence and proliferation of informal means of co-operation has challenged the monopoly of traditional forms of international law-making. This shift to informality has forced modern international legal scholarship to rethink whether, and if so to what extent, the international legal order can adapt to and assimilate the sweeping changes on the international plane. Different accounts of how the discipline ought to come to terms with the phenomenon of informal international law have been offered; however, these often tend to neglect the practice of the EU and its principal judicial organ. In this light, the present contribution purports to examine how the CJEU has treated informal law in its practice with a view to ascertaining the Court’s contribution to the continuing development of the doctrine of international law-making. The main argument advanced here is that the CJEU has recourse to a range of tools for factoring in new social developments, while keeping clear boundaries between law and non-law. It is asserted that current theorizing on the topic should engage more strongly in this practice since it attests to international law’s ability to cope with informality, thereby lending normative and explanatory force to theoretical approaches that insist on retaining the distinction between law and non-law.