This article assesses how, 50 years after the ECJ delivered its judgment in Van Gend and Loos (VGL), the doctrine of direct effect of international law has fared outside the European Union. While obviously the core of VGL (that is, that it is EU law, not national law, which requires direct effect) is not replicated anywhere else in the world, the courts of a considerable number of states have been able to give direct effect to international law. Against the background of an exceedingly heterogeneous practice, this article argues that the concept of direct effect is characterized by a fundamental duality. Direct effect may function as a powerful sword that courts can use to pierce the boundary of the national legal order and protect individual rights where national law falls short. But more often than not, the conditions of direct effect legitimize the non-application of international law and shield the national legal order from international law. International law provides support for both functions. But above all, it defers the choice between these functions to national courts. The practice of direct effect of international law exposes how national courts play a critical political function at the intersection of legal orders.