This article comments on the recent UK Supreme Court decision on the legality of triggering art.50. It sets out the background to the decision and explains and evaluates the differences between the majority and the minority. It argues that the decision, in one sense, did not live up to the expectations generated by its publicity. It drew on longstanding principles of UK constitutional law and its outcome appears unlikely to delay or condition the exercise of art.50. Nevertheless, the majority focused on the constitutional impact of joining the EU and reinforced both that it is for UK law to determine the relationship between UK law and EU law, and that constitutional principles of the UK may limit the transfer of sovereignty from the UK to the EU. These elements may have more long-term consequences for EU law.