The margin of appreciation, as a doctrine of international law, has a great future behind it. It was once thought to be the panacea that would solve international law’s problems, but has in fact diminished in importance in international law. Contrary to what is often argued, the doctrine of the margin of appreciation originated in early public international law, not in Continental domestic public law. In the course of the twentieth century, international law discarded the doctrine. The preferred standard of review, as the International Court set out in Whaling in the Antarctic, is ‘an objective one’. In the sphere where the margin of appreciation is most famously in operation, the law of European human rights, it is being supplanted by the doctrine of subsidiarity. The margin of appreciation is, in international law, an aberration. It is time we treated it as such. This article was presented as the inaugural CJICL Young Scholars’ Lecture in February 2015, held at the Lauterpacht Centre for International Law, University of Cambridge.