Series Editor’s Preface: Jesse James, Laws of All the Greeks

What are the sources of the law that applies in the international realm? We tend to believe that something is law if it has been made by our legislature, but there is no legislature above or beyond the state. When it comes to public international law, the reigning doctrine as contained in the Statute of the International Court of Justice is that treaties, state practice, and the “general principles of law recognized by civilized nations” are the sources that determine the validity of international law. The extent to which there is an inbuilt hierarchy of these sources of law is a matter of contention, but treaties tend to have a higher status than does customary law at least for the contracting parties, and both treaties and custom prevail whenever they conflict with general principles of law, because these general principles, although originally tightly connected to the natural- and Roman-law matrix from which the early modern law of nations arose, are nowadays merely perceived as a plug to fill in gaps in treaty and customary law. Needless to say, this is a highly positivist way of looking at things, and it is only via the idea of ius cogens, or so-called peremptory norms, that the voluntarist framework of treaty and custom receives any kind of constraint.