The emptiness at the heart of international law

“What is not prohibited is allowed” is the principle at the heart of international law. Yet the principle is empty. It originates in the Lotus judgment of the Permanent Court of International Justice of 1927 where Turkey was allowed to prosecute a French citizen at the expense of the authority of France to have exclusive jurisdiction. This article recounts the history of “what is not prohibited is allowed” and explains where it has led us astray and where it is in the process of doing so. It recalls that the intention of the creators of the Permanent Court of International Justice was very different, namely that equitable balancing would take place when no specific international law norm could be identified. The article suggests how, through an Advisory Opinion by the International Court of Justice, equitable balancing can be re‐established as the fallback principle when international law is otherwise silent.