There is a certain paradoxical character about the concept of lex ferenda as an element of legal discussion, since the defining feature of lex ferenda is that, whatever else it may be, it is not part of positive law. Yet the term is at times found useful in doctrinal discussion; it was the subject of a penetrating essay, some 20 years ago, by the late Professor Michel Virally, and the time is perhaps ripe for its re-examination, in the light, in particular, of some more recent decisions of the International Court of Justice. Lex ferenda serves as a label for something which has at least conceptual existence, as a contrast or opposite to lex lata, the law that exists and obliges the subjects of law to adopt, or to refrain from, certain defined courses of conduct in certain defined circumstances. The term is not, however, a mere antithesis, in the sense of referring to something or everything that is not law: the force of the Latin gerund (‘delenda est Carthago’) is that the term refers to something that in some sense ought to be law, but is not. There are of course numerous possible ideas and rules which might be law, but of these many not only are not law, but are not even potential law, inasmuch as they would not be desirable as law, and would therefore not fall into the narrower, more precise, category of lex ferenda.