Courts in the United Kingdom and South Africa have recently issued important rulings that have constrained the executive's authority to withdraw from treaties in those countries. This essay considers whether these rulings might offer insights for treaty exit issues in the United States. We first provide an overview of U.S. law and practice regarding the termination of international agreements. We next summarize the U.K. and South African decisions, which required parliamentary approval for pulling out of treaties establishing the European Union and the International Criminal Court (ICC), respectively. Finally, we consider the relevance of these rulings for treaty withdrawals in the United States. We conclude that they are unlikely to offer much guidance, both because of differences in the three countries' constitutions and because the reasoning of the U.K. and South African courts do not engage with the central arguments made in the United States concerning the President's unilateral authority to withdraw from treaties.

In “the constitutional case of the century,” the U.K. Supreme Court concluded that the Government did not possess the prerogative power to withdraw from the European Union. However, while it may be clear from the decision that legislation was required to empower the Government to notify the European Union of its intention to leave, the scope of the Court's reasoning in Miller is otherwise uncertain. At its broadest, the decision would apply to the withdrawal from any treaty that had created rights for individuals, regardless of whether such a treaty had been implemented into domestic law or not. At its narrowest, it only applies to the EU Treaties, which created a set of arrangements in international law that are so esoteric, they are unique to the European Union. To demonstrate how one judgment can generate such a range of interpretations, this essay unravels the different strands of argument running through the decision and considers the criticisms leveled by scholars. It will argue that whether U.K. law requires legislation to withdraw from a treaty depends upon the extent to which that treaty creates rights in domestic law, the constitutional importance of the legislation incorporating the treaty into U.K. law, and the circumstances in which a legal challenge to the use of the prerogative arises. Miller provides no general answer, merely a series of questions.

On March 29, 2017, the U.K. Government triggered Article 50 of the Treaty on European Union (TEU) on withdrawal from the European Union following a referendum on June 23, 2016 in which 51.89 percent voted for the United Kingdom to leave the European Union. As a hybrid provision, the much-discussed withdrawal provision in Article 50 TEU is part of EU law yet also anchored in public international law. Although the European Union is a unique, supranational organization that creates rights for individuals that are directly effective in national law, its member states created the European Union based on traditional treaties under international law.

An uneasy equilibrium exists with respect to how the United States exits international agreements. In general, exit is easy as a matter of legal doctrine but, for important agreements, difficult as a matter of political practice. While presidents can withdraw the United States from most major international agreements, they have done so only rarely—and never yet with deep costs to the stability of our world order.

The questions surrounding the legality of states’ withdrawal from international treaties have traditionally received far less attention than those concerning states’ joining of treaties, from both the domestic and international legal perspectives. This neglect is now changing rapidly. In this contribution I focus on South Africa's stalled exit from the International Criminal Court (ICC) and the fundamental questions of constitutional and international law that arise from the episode.

Constitutional courts in Latin America have used judicial review to enhance the relevance of international law in recent years. Some scholars even speak of a growing “constitutionalization of international law” in the region. But these domestic courts can also act as gatekeepers that blunt or entirely deflect the domestic impact of international law. This essay explores three recent episodes in which constitutional courts joined or led efforts to escape treaty obligations: the Venezuelan Supreme Court's judgment urging the Chávez Administration to denounce the American Convention of Human Rights on constitutional grounds, which Chavez then did in 2012 (a court-inspired treaty exit); the Colombian executive's 2013 petition to have Colombia's acceptance of the International Court of Justice's (ICJ's) jurisdiction under the Pact of Bogotá declared unconstitutional (a court-legitimated treaty exit); and the Dominican Republic (DR) Constitutional Tribunal's 2014 judgment holding that the DR's acceptance of the jurisdiction of the Inter-American Court of Human Rights (IACtHR) had been unconstitutional (a court-led treaty exit).

When states withdraw from bilateral investment treaties or denounce multilateral treaties related to foreign investment, a range of intersecting questions arise in domestic and international law. Recent developments have demonstrated potential incongruities between domestic and international approaches to investment protection, including as regards the effectiveness of withdrawal and the implications for existing investments. This essay reflects on international and domestic disputes involving the withdrawal of the Russian Federation from participation in the Energy Charter Treaty (ECT) to highlight these interactions. These issues have become particularly pertinent today because more than 1,500 international investment agreements (IIAs) are nearing expiry of their initial term, providing an opportunity for termination. Moreover, some states have begun to terminate or denounce investment treaties, while many more are engaging in a process of renegotiation and reform. The Russian case study also highlights the potentially far-reaching effects of a state simply signing a treaty, even many years after the state has expressed its decision to withdraw from it, and notwithstanding tensions with the domestic legal framework.