Regardless of its views about Iran’s regional policies and actions—or, indeed, about the policies and actions of its regional rivals such as Israel and Saudi Arabia—the US withdrawal from the JCPOA is ill-conceived and regrettable for many reasons. It undermines the value of multilateral diplomacy and raises questions about the sanctity and sustainability of interstate agreements. Furthermore, it challenges the authority of the UN Security Council, which has unanimously passed a resolution endorsing the JCPOA and calling on all UN member states as well as regional and international organizations to take action to support the agreement’s implementation. US withdrawal from the JCPOA risks seriously weakening trust and confidence in international institutions and arrangements that are essential parts of the global security architecture. In particular, the US action undermines the global effort for nuclear non-proliferation by sabotaging an important and effective anti-proliferation agreement. It is to be hoped that the remaining parties to the JCPOA will find ways to support its continued implementation.