¹ For additional discussion, see Helfer, Laurence R, ‘Exiting Treaties’ (2005) 91 Virginia Law Review 1579, 1592Google Scholar.

² I am unaware of any international instrument that expressly prohibits withdrawal. However, several important multilateral treaties and charters of international organisations have no provision for exit. The Vienna Convention on the Law of Treaties ((entered into force 27 January 1980) 1155 UNTS 331), art 56(1), creates a presumption against denunciation or withdrawal, which may be overcome by ‘establish[ing] that the parties intended to admit the possibility of denunciation or withdrawal’ or that a ‘right of denunciation or withdrawal may be implied by the nature of the treaty’. For additional discussion, see Helfer, Laurence R, ‘Terminating Treaties’ in Hollis, Duncan B (ed), The Oxford Guide to Treaties (Oxford University Press 2012) 634Google Scholar; Pergantis, Vassilis, The Paradigm of State Consent in the Law of Treaties: Challenges and Perspectives (Edward Elgar 2017) 154–88Google Scholar.

³ Feinberg, Nathan, ‘Unilateral Withdrawal from an International Organization’ (1963) 39 British Yearbook of International Law 189Google Scholar; Schwelb, Egon, ‘Withdrawal from the United Nations: The Indonesian Intermezzo’ (1967) 61 American Journal of International Law 661CrossRefGoogle Scholar.

⁴ Henkin, Louis, How Nations Behave (Columbia University Press 1979) 47Google Scholar (‘It is probably the case that almost all nations observe almost all principles of international law and almost all of their obligations almost all of the time’).

⁵ See, eg, United Nations Treaty Section, Final Clauses of Multilateral Treaties: Handbook (United Nations Publications 2003)Google Scholar.

⁶ Bilder, Richard B, Managing the Risks of International Agreement (The University of Wisconsin Press 1981)Google Scholar.

⁷ Koremenos, Barbara and Nau, Allison, ‘Exit, No Exit’ (2010) 21 Duke Journal of Comparative International Law 81, 95–100Google Scholar (reviewing examples of waiting and notice periods in treaty exit clauses).

⁸ States sometimes volunteer an explanation for their decision to exit, such as where a treaty conflicts with the state's constitution or other international law obligations: see, eg, Declaratory Statement by the Republic of South Africa on the Decision to Withdraw from the Rome Statute of the International Criminal Court, 19 October 2016, C.N.786.2016.TREATIES-XVIII.10 (Depositary Notification 2016), 2 (describing the ‘conflicting international law obligations’ that precipitated South Africa's notice of withdrawal from the Rome Statute).

⁹ The White House, ‘Statement by President Trump on the Paris Climate Accord’, 1 June 2017, https://www.whitehouse.gov/the-press-office/2017/06/01/statement-president-trump-paris-climate-accord.

¹⁰ Paris Agreement (entered into force 4 November 2016), http://unfccc.int/paris_agreement/items/9485.php.

¹¹ Stephen P Mulligan, ‘Withdrawal from International Agreements: Legal Framework, the Paris Agreement, and the Iran Nuclear Agreement’, Congressional Research Service, 4 May 2018, 19, https://fas.org/sgp/crs/row/R44761.pdf.

¹² (entered into force 21 March 1994) 1771 UNTS 107.

¹³ Paris Agreement (n 10) art 28(3) (‘Any Party that withdraws from the [Framework] Convention shall be considered as also having withdrawn from this Agreement.’).

¹⁴ Mulligan (n 11) 19–20; Jonathan B Wiener, ‘Climate Policy in the New US Administration’, Climate Economics Chair Policy Brief No 2017-02, 5 June 2017, 3–4, https://www.chaireeconomieduclimat.org/wp-content/uploads/2017/06/17-06-06-Policy-Brief-2017-02-Wiener-Climate-Policy-in-the-new-US-administration.pdf.

¹⁵ See, eg, Guzman, Andrew T, ‘The Design of International Agreements’ (2005) 16 European Journal of International Law 579CrossRefGoogle Scholar; Guzman, Andrew T, ‘International Tribunals: A Rational Choice Analysis’ (2008) 157 University of Pennsylvania Law Review 171Google Scholar; Raustiala, Kal, ‘Form and Substance in International Agreements’ (2005) 99 American Journal of International Law 581CrossRefGoogle Scholar.

¹⁶ Not all exit threats are opportunistic. Sometimes states threaten exit to refocus the organisation on its primary mandate. For example, the United States gave notice of its intention to leave the ILO in the late 1970s, arguing that the organisation had become unduly politicised. Had the US in fact withdrawn, the organisation would have lost a significant percentage of its funding. Partly in response to this threat, the ILO changed its policies before the two-year notice period expired and the US remained a member of the organization: see Imber, Mark F, The USA, ILO, UNESCO and IAEA: Politicization and Withdrawal in the Specialized Agencies (Palgrave Macmillan 1989)CrossRefGoogle Scholar; Melanson, Richard A, ‘Human Rights and the American Withdrawal from the ILO’ (1979) 1 Universal Human Rights 43CrossRefGoogle Scholar.

¹⁷ Koremenos, Barbara, The Continent of International Law: Explaining Agreement Design (Cambridge University Press 2016)CrossRefGoogle Scholar.

¹⁸ Koremenos finds that treaties that address ‘enforcement problems’ are more likely to include longer notice periods than other types of international agreement, while treaties that address underlying ‘commitment problems’ are more likely to have longer waiting periods: ibid 145.

¹⁹ Helfer (n 1) 1599–601; Meyer, Timothy, ‘Power, Exit Costs, and Renegotiation in International Law’ (2010) 51 Harvard International Law Journal 379Google Scholar.

²⁰ Helfer (n 1) 1602.

²¹ Helfer, Laurence R, ‘Flexibility in International Agreements’ in Dunoff, Jeffrey and Pollack, Mark A (eds), Interdisciplinary Perspectives on International Law and International Relations: The State of the Art (Cambridge University Press 2013) 175Google Scholar.

²² For a discussion of the reputational consequences of exit, see Helfer (n 1) 1590, 1621–29; Brewster, Rachel, ‘Exit from Trade Agreements: A Reputational Analysis of Cooperation and Fairness’ (2018) 21 Journal of International Economic Law 379CrossRefGoogle Scholar.

²³ Politakis, George P, ‘Night Work of Women in Industry: Standards and Sensibility’ (2001) 140 International Labour Review 403CrossRefGoogle Scholar.

²⁴ Helfer (n 21) 185.

²⁵ Helfer (n 1) 1645–47.

²⁶ (entered into force 23 March 1976) 999 UNTS 171.

²⁷ Pact of San José, Costa Rica (entered into force 18 July 1978) 1144 UNTS 123.

²⁸ Helfer, Laurence R, ‘Overlegalizing Human Rights: International Relations Theory and the Commonwealth Caribbean Backlash against Human Rights Regimes’ (2002) 102 Columbia Law Review 1832CrossRefGoogle Scholar.

²⁹ Pratt v The Attorney General for Jamaica [1993] UKPC 1; [1993] 2 AC 1 (Jamaica).

³⁰ Helfer (n 28) 1882–84.

³¹ Soley, Ximena and Steininger, Silvia, ‘Parting Ways or Lashing Back? Withdrawals, Backlash and the Inter-American Court of Human Rights’ (2018) 14 International Journal of Law in Context 237CrossRefGoogle Scholar, 241 (internal quotations omitted); see also Madsen, Mikael Rask, Cebulak, Pola and Wiebusch, Micha, ‘Backlash Against International Courts: Explaining the Forms and Patterns of Resistance to International Courts’ (2018) 14 International Journal of Law in Context 5CrossRefGoogle Scholar.

³² Contesse, Jorge, ‘Resisting Inter-American Human Rights Law’ (2019) 44 Yale Journal of International LawGoogle Scholar (forthcoming).

³³ Ministry of Foreign Affairs (Venezuela), ‘Notificación de Denuncia’ and ‘Fundamentación que sustenta la denuncia de la República Bolivariana de Venezuela de la Convención Americana sobre Derechos Humanos presentada a la Secretaría General de la OEA’, 10 September 2012, http://www.minci.gob.ve/wp-content/uploads/2013/09/Carta-Retiro-CIDH-Firmada-y-sello.pdf.

³⁴ Soley and Steininger (n 31) 252.

³⁵ ‘Venezuela Delivers Letter Formalizing Exit from “Coercive” OAS’, Telesur, 28 April 2017, https://www.telesurtv.net/english/news/Venezuela-Delivers-Letter-Formalizing-Exit-From-Coercive-OAS-20170428-0019.html.

³⁶ Graeme Smith, ‘African Leaders Plan Mass Withdrawal from International Criminal Court’, The Guardian, 31 May 2017. To date, only Burundi has withdrawn from the Rome Statute; notices of withdrawal filed by the Gambia and South Africa were later withdrawn: Ssenyonjo, Manisuli, ‘State Withdrawal Notifications from the Rome Statute of the International Criminal Court: South Africa, Burundi and the Gambia’ (2018) 29 Criminal Law Forum 63CrossRefGoogle Scholar. The situation in South Africa is discussed below.

³⁷ Peinhardt, Clint and Wellhausen, Rachel L, ‘Withdrawing from Investment Treaties but Protecting Investment’ (2016) 7 Global Policy 571, 572CrossRefGoogle Scholar; Nicholas Peacock and Nihal Joseph, ‘Mixed Messages to Investors as India Quietly Terminates Bilateral Investment Treaties with 58 countries, Arbitration Notes’, Herbert Smith Freehills, 16 March 2017, https://hsfnotes.com/arbitration/2017/03/16/mixed-messages-to-investors-as-india-quietly-terminates-bilateral-investment-treaties-with-58-countries.

³⁸ Helfer, Laurence R and Showalter, Anne E, ‘Opposing International Justice: Kenya's Integrated Backlash Strategy Against the ICC’ (2017) 17 International Criminal Law Review 1CrossRefGoogle Scholar; Roberts, Anthea, ‘Incremental, Systemic, and Paradigmatic Reform of Investor-State Arbitration’ (2018) 112 American Journal of International Law 410CrossRefGoogle Scholar.

³⁹ See, eg, Dapo Akande, ‘Withdrawal from the United Nations: Would It Have Been Lawful for the Philippines?’, EJIL: Talk!, 19 September 2016, https://www.ejiltalk.org/can-the-philippines-withdraw-from-the-un; Inken von Borzyskowski and Felicity Vabulas, ‘The Costs of Membership Withdrawal from Intergovernmental Organizations’, paper prepared for the Political Economy of International Organizations Conference, University of Wisconsin, 8–10 February 2018, http://wp.peio.me/wp-content/uploads/2018/02/Borzyskowski-and-Vabulas_Consequences-of-Withdrawal-paper-53.pdf; Jennifer Trahan, ‘Reflections on Burundi's Withdrawal from the International Criminal Court’, Opinio Juris, 31 October 2017, http://opiniojuris.org/2017/10/31/reflections-on-burundis-withdrawal-from-the-international-criminal-court.

⁴⁰ Jed Odermatt, ‘Brexit and International Law’, EJIL: Talk!, 4 July 2016, https://www.ejiltalk.org/brexit-and-international-law.

⁴¹ Rachel Ansley, ‘Are Trump's Tariffs Aimed at the WTO?’, Atlantic Council, 6 March 2018, http://www.atlanticcouncil.org/blogs/new-atlanticist/are-trump-s-tariffs-aimed-at-the-wto; Philip Crowther, ‘Trump Threatens to Quit NATO: White House Official’, France 24, 19 May 2017, http://www.france24.com/en/20170518-white-house-official-trump-threatens-leave-nato-usa-g7-russia; Ana Swanson and Kevin Granville, ‘What Would Happen if the U.S. Withdrew from Nafta’, The New York Times, 12 October 2017, https://www.nytimes.com/2017/10/12/business/economy/what-would-happen-if-the-us-withdrew-from-nafta.html.

⁴² See, eg, Helfer, Laurence R, ‘Introduction to Symposium on Treaty Exit at the Interface of Domestic and International Law’ (2017) 111 AJIL Unbound 425CrossRefGoogle Scholar.

⁴³ Bothe, Michael, ‘Article 46, Convention of 1969’ in Corten, Olivier and Klein, Pierre (eds), The Vienna Convention on the Law of Treaties: A Commentary (Oxford University Press 2011) 1090, 1091Google Scholar (‘From the point of view of efficiency, it is essential that international cooperation, at least to a large extent, constitutes a prerogative of the executive’).

⁴⁴ Blix, Hans and Emerson, Jirina H, The Treaty Maker's Handbook (Dag Hammarskjoeld Foundation 1973) 114–16Google Scholar.

⁴⁵ VCLT (n 2) art 7; see also Robert Kolb, The Law of Treaties: An Introduction (Edward Elgar 2016) 38.

⁴⁶ International Law Commission, Draft Articles on the Law of Treaties with Commentaries, 1966(II) Yearbook of the International Law Commission 264; see also ‘Second Report on the Law of Treaties by Sir Humphrey Waldock’, 1963(II) Yearbook of the International Law Commission 85 (‘The power to annul, terminate, withdraw from or suspend treaties, no less than the power to conclude treaties, forms part of the treaty-making power of the State’).

⁴⁷ VCLT (n 2) art 67(2).

⁴⁸ Helfer, Laurence R, ‘Treaty Exit and Intra-Branch Conflict at the Interface of International and Domestic Law’ in Bradley, Curtis A (ed), Oxford Handbook of Comparative Foreign Relations Law (Oxford University Press 2019)Google Scholar (forthcoming).

⁴⁹ The constitutions of Bosnia and Herzegovina, Guatemala and Syria appear to authorise unilateral executive withdrawal. Chile's constitution requires the executive to consult with the legislature.

⁵⁰ In several of the 39 countries, the legislature must approve exit from all international agreements: eg, Constitution of Moldova, Title III, 27 August 1994 (rev 2016), Ch IV, s 1(66) (granting the Parliament the power ‘to ratify, terminate, suspend and repeal … international treaties’). In others, the constitution indicates the subject matter of treaties for which withdrawal requires parliamentary assent or provides that ratification and denunciation are governed by the same procedures: see, eg, Constitution of Estonia, 28 June 1992 (rev 2015), Ch IX, art 121 (Parliament ‘shall ratify and denounce treaties … which alter state borders; the implementation of which requires the passage, amendment or repeal of Estonian laws; by which the Republic of Estonia joins international organizations or unions; by which the Republic of Estonia assumes military or proprietary obligations; in which ratification is prescribed’); Constitution of Kosovo, 15 June 2008 (rev 2016), Ch I, art 18 (‘withdrawal from international agreements follows the same decision-making process as the ratification of international agreements’).

⁵¹ See, eg, Law No 421-Z on Treaties of the Republic of Belarus, 23 July 2008, art 41 (listing categories of treaties that may be denounced by, respectively, the National Assembly, the President, and the Council of Ministers).

⁵² R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5; [2017] 2 WLR 583.

⁵³ ibid [60].

⁵⁴ ibid [86].

⁵⁵ ibid [78], [82].

⁵⁶ Young, Alison L, ‘Brexit, Miller, and the Regulation of Treaty Withdrawal: One Step Forward, Two Steps Back?’ (2017) 111 AJIL Unbound 434CrossRefGoogle Scholar.

⁵⁷ The government's decision to leave the ICC was triggered by fallout from the visit by Sudanese President Omar al-Bashir to South Africa in 2015. All state parties to the Rome Statute are under an obligation to arrest individuals, such as al-Bashir, who have been indicted by the ICC. Al-Bashir, however, claims immunity from prosecution as a sitting head of state under both treaties and customary international law. The government asserted that withdrawing from the ICC was intended to resolve these ‘conflicting international law obligations’: Depositary Notification 2016 (n 8) 2.

⁵⁸ Democratic Alliance v Minister of International Relations and Cooperation 2017 1 SACR 623 (GP).

⁵⁹ Constitution of South Africa, 1996, s 231. According to the first clause of s 231, ‘[t]he negotiating and signing of all international agreements is the responsibility of the national executive’. However, s 231(2) provides that treaties signed by the executive do not bind South Africa on the international plane until ‘after [they have] been approved by resolution in both the National Assembly and the National Council of Provinces’.

⁶⁰ Democratic Alliance (n 58) 47.

⁶¹ ibid.

⁶² ibid [51].

⁶³ ibid [56]. For additional discussion, see Woolaver, Hannah, ‘Domestic and International Limitations on Treaty Withdrawal: Lessons from South Africa's Attempted Departure from the International Criminal Court’ (2017) 111 AJIL Unbound 450CrossRefGoogle Scholar.

⁶⁴ Rome Statute of the International Criminal Court: South Africa: Withdrawal of Notification of Withdrawal, C.N.121.2017.TREATIES-XVIII.10 (Depositary Notification 2017), 7 March 2017.

⁶⁵ Theresa Reinold, ‘African Union v International Criminal Court: Episode MLXIII (?)’, EJIL: Talk!, 23 March 2018, https://www.ejiltalk.org/african-union-v-international-criminal-court-episode-mlxiii.

⁶⁶ For a more extensive discussion of the different types of bifurcation, see Helfer (n 48).

⁶⁷ The VCLT provides that an exiting state is released ‘from any obligation further to perform’ the treaty ‘from the date when such denunciation or withdrawal takes effect’: VCLT (n 2) art 70(1)(a), 70(2). Withdrawal does not, however, abrogate the state's obligations under customary international law: VCLT art 43; Helfer, Laurence R, ‘Exiting Custom: Analogies to Treaty Withdrawals’ (2010) 21 Duke Journal of Comparative & International Law 65, 71Google Scholar.

⁶⁸ Helfer (n 48); see also Villiger, Mark E, Commentary on the 1969 Vienna Convention on the Law of Treaties (Martinus Nijhoff 2009) 588Google Scholar (‘if a State representative who is competent under international law expresses the consent of the State to a treaty, that State is bound to its international obligations under the treaty’).

⁶⁹ Villiger, ibid 591 (‘When expressions of consent are exchanged, the other State will normally have to accept its partner's declaration as to competence … Any closer questioning of another State's internal handling of a treaty would, in fact, be regarded as interference in State affairs’).

⁷⁰ See, eg, Maria O'Sullivan, ‘Nauru's Renunciation of Appeals to the High Court – Lawfulness and Implications’, Castan Centre for Human Rights Law: The Official Blog, 5 April 2018, https://castancentre.com/2018/04/05/naurus-renunciation-of-appeals-to-the-high-court-lawfulness-and-implications (arguing that the Nauru Appeals Act, which implements a 1976 agreement between Australia and Nauru authorising appeals from the Nauru Supreme Court to the Australian High Court, continued in force following the Nauru executive's denunciation of the agreement).

⁷¹ See, eg, Banful v Attorney-General [2017] Accra-AD 1 (Ghana) (invalidating a bilateral agreement between the US and Ghana to resettle two Yemeni detainees from the Guantanamo Bay detention centre, where the agreement had not been approved by parliament in contravention of the constitution); Namah v Pato [2016] PJSC 13 (Papua New Guinea) (holding unconstitutional the detention of asylum seekers and refugees pursuant to a memorandum of understanding between Papua New Guinea and Australia and ordering the government to cease the illegal detention, in effect rendering the memorandum domestically unenforceable); Relativo a la acción directa de inconstitucionalidad incoada contra el Instrumento de Aceptación de la Competencia de la Corte Interamericana de Derechos Humanos, Judgment No TC/0256/14 (Constitutional Tribunal, Dominican Republic 2014) (the President's declaration accepting the jurisdiction of the Inter-American Court of Human Rights was unconstitutional and invalid because it lacked congressional approval).

⁷² Waibel, Michael, ‘Brexit and Acquired Rights’ (2017) 111 AJIL Unbound 440CrossRefGoogle Scholar.

⁷³ Alex Barker, ‘The €60 Billion Brexit Bill: How to Disentangle Britain from the EU Budget’, Centre for European Reform, 6 February 2017.

⁷⁴ VCLT (n 2) art 70(1)(b). For further discussion, see Waibel (n 72) 440–41.

⁷⁵ Luke Eric Peterson, ‘What Have We Learned from the First Wave of Post-denunciation ICSID Claims against Venezuela – and Why Do Investors Keep Suing Venezuela There?’, Investment Arbitration Reporter, 30 November 2017, http://tinyurl.com/y7qtqkp2; Voon, Tania and Mitchell, Andrew D, ‘Ending International Investment Agreements: Russia's Withdrawal from Participation in the Energy Charter Treaty’ (2017) 111 AJIL Unbound 461CrossRefGoogle Scholar; see also Helfer (n 67) 78–79 (discussing case law of the Inter-American Court and Commission on Human Rights following Trinidad and Tobago's withdrawal).

⁷⁶ Perhaps the most well-known example of post-withdrawal obligations are the ‘survival clauses’ of investment treaties, which continue to protect existing investors and investments ‘for ten to twenty years after either treaty party terminates’: Roberts, Anthea, ‘Triangular Treaties: The Extent and Limits of Investment Treaty Rights’ (2015) 56 Harvard International Law Journal 353, 386–87Google Scholar.

⁷⁷ Depositary Notification 2017 (n 64).

⁷⁸ VCLT (n 2) art 67(2) (‘Any act … withdrawing from … a treaty … shall be carried out through an instrument communicated to the other parties. If the instrument is not signed by the Head of State, Head of Government or Minister for Foreign Affairs, the representative of the State communicating it may be called upon to produce full powers’); ibid art 68 (providing, inter alia, that an instrument or notification of withdrawal ‘may be revoked at any time before it takes effect’).

⁷⁹ See Antonios Tzanakopoulos, ‘Article 68, Convention of 1969’, in Corten and Klein (n 43) 1564.

⁸⁰ Paul Eden, ‘Can a Notification under Article 50 TEU Be Unilaterally Withdrawn?’, UK Trade Policy Observatory Blog, 17 March 2017, https://blogs.sussex.ac.uk/uktpo/2017/03/17/can-a-notification-under-article-50-teu-be-unilaterally-withdrawn; Jake W Rylatt, ‘The Irrevocability of an Article 50 Notification: Lex Specialis and the Irrelevance of the Purported Customary Right to Unilaterally Revoke’, UK Constitutional Law Association Blog, 27 July 2016, https://ukconstitutionallaw.org/2016/07/27/jake-rylatt-the-irrevocability-of-an-article-50-notification-lex-specialis-and-the-irrelevance-of-the-purported-customary-right-to-unilaterally-revoke.

⁸¹ Charles Streeten, ‘Putting the Toothpaste Back in the Tube: Can an Article 50 Notification Be Revoked?’, UK Constitutional Law Association Blog, 13 July 2016, https://ukconstitutionallaw.org/2016/07/13/charles-streeten-putting-the-toothpaste-back-in-the-tube-can-an-article-50-notification-be-revoked.