What Might (Finally) Kill the Jus ad Bellum?

There is a long tradition of international relations and legal scholars warning of the demise of the jus ad bellum—the body of international law that governs when states may use force across national borders. I argue in this Lecture, presented at The University College London Faculty of Laws in October 2020, that these warnings have mostly been wrong. The reason they have been wrong is that they have misdiagnosed the main threat to the jus ad bellum, or at least, they have myopically focused on and grossly overstated the seriousness of a particular kind of threat. And in doing so, they have diverted attention away from other challenges that might actually push the contemporary jus ad bellum to the breaking point—and that we might now confront.