Recent world developments pose a direct challenge to the authority and effectiveness of international law. The actions of Russia in Ukraine, and China in the South China Sea, represent a particular threat. These actions are in clear violation of international law, involving the threat or use of armed force and the seizure of territory, and Russia and China are permanent members of the UN Security Council – the body charged by the international community with maintaining international peace and security. Putting further potential strain on the international legal order is the marked shift towards nationalism in many states, most notably the United States under Donald Trump. This article argues that the international community should not accept these developments as inevitable. Support for multilateralism over isolationism and unequivocal condemnation of breaches of international law are needed now more than ever.