Jus Cogens: A Complex Case of Constitutional Reasoning in International Law

Abstract

Article 53 of the Vienna Convention on the Law of Treaties famously introduced a special class of international legal rules - jus cogens norms - without specifying its content. The paper proceeds by adopting the heuristic framework of constitutionalization of international law, arguing that jus cogens norms contribute to at least two constitutionalist functions - that of limiting the international governance and hierarchizing international legal order. Hence, it is possible to argue that jus cogens reasoning is a specific type of constitutional reasoning. Despite stipulated formal qualities of jus cogens norms, in trying to establish their content state actors are in the situation similar to constitutional adjudicators dealing with underdetermined legal content of a constitutional text. What directs the process of jus cogens reasoning is, thus, the particular nature of the subject-matter with which those norms deal. The last part of the paper provides the analytical reconstruction of the jus cogens constitutional reasoning, focusing on the process of ascertainment, which is to be taken by the community of states. It is argued that what ascertainment requires is, inter alia, resorting to a unique interpretative tool - reverse teleological argument - with the use of which the state actor can extract from the fundamental values of international legal order a class of peremptory norms of international law.