2. Sherlock Holmes and the Mystery of Jus Cogens

The doctrine of jus cogens attracts fierce advocates as well as strong sceptics, who debate the nature, functions and even the existence of such norms. Like Sherlock Holmes, the idea of jus cogens emerged as a concept in the imagination of writers. Over time both Sherlock Holmes and jus cogens have generated widespread belief in their reality, but it is a reality that is subjectively shaped by each follower. Early publicists creating and developing international law posited the existence of extra-consensual norms that constrained the exercise of state sovereignty, a theory that emerged in large part from Christian theology with its notions of overriding divine law. Later publicists argued that non-derogable norms originate either in natural law, ‘necessary’ law, the ‘dictates of the public conscience’, ‘universal law’, or international moral imperatives. Some recent scholars rely on the Vienna Conventions on the Law of Treaties to argue to the contrary that norms of jus cogens do not fundamentally differ from other international rules in their origin; they emerge only from state consent, being identified ‘by the international community of states as a whole’ as peremptory norms. Within the literature as to the origin of jus cogens, in the absence of state practice, theorists differ in their views of the functions the concept serves, some arguing that it is limited in application to treaty law. Others assert that such norms act to place absolute limits on the conduct of states, governments and individuals and establish a hierarchy of norms. This article examines the origin of jus cogens in doctrine and the scant evidence to be found in state practice. It also examines the functions of jus cogens, questioning whether these remain largely literary and theoretical, with an impact like Sherlock Holmes that derives primarily from belief in its existence.