This essay intends to shed light on the nature of the Joint Comprehensive Plan of Action (JCPoA) concerning Iran’s Nuclear Programme. It argues that the JCPoA is not a treaty but a mere political commitment, to which however some legally binding effects have been attached by Security Council Resolution 2231 (2015). As a consequence, this essay also submits that, in ceasing its participation in the JCPoA and re-imposing sanctions against Iran under the 2018 Presidential Memorandum, the United States breached Resolution 2231 (2015) and thus committed an internationally wrongful act. In this connection, the reactions progressively enacted by Iran — and culminated in the restoration in 2020 of its pre-2015 Nuclear Programme — may find a justification. With the Security Council failing to take action, the role of the International Court of Justice deserves special attention. Indeed, Iran has started proceedings before the Court in 2018 alleging that, by reactivating the sanctions regime, the United States violated the 1955 bilateral Treaty of Amity, Economic Relations, and Consular Rights.