This article explores how the concept of jus cogens is understood and practiced in the field of international law. While the concept has gained mass acceptance and recognition, the actual legal significance and application is still very much unclear. In Article 53 of the Vienna Convention on the Law of Treaties, peremptory norms are defined as those which are ‘non-derogable’ but nevertheless require the ‘acceptance and recognition’ from the international community as a whole. This process of acceptance and recognition had to be developed through state practice and judgments from international courts and tribunals. Accordingly, this article examines how jus cogens has been interpreted by those actors, without ignoring the contributions from academic scholarship and reports of the International Law Commission. Through analysing these sources, it becomes clear that the task of clarifying the content and legal meaning of the concept is continuously being deferred amongst the relevant actors. After demonstrating this tendency, the remaining sections of the article discuss why this is happening, whether it is forth fixing and if so how that change could come about.