Why do states commit to the Treaty on the Prohibition of Nuclear Weapons?

ABSTRACT

On January 22, 2021, the Treaty on the Prohibition of Nuclear Weapons (TPNW) entered into force. The aim of the treaty is to delegitimize nuclear weapons by strengthening the antinuclear norm. The aim comes with the expectation that this will gradually contribute to an environment in which nuclear weapons can be eliminated because they are unacceptable instruments of statecraft. However, the effectiveness of antinuclear norms has been contested in discussions around the TPNW. In particular, the question of how norms operate within smaller identity communities has attracted the attention of scholars studying commitment to international treaties. By using a mixed-methods research design, this article adds to the ongoing discussion by exploring the conditions under which regional normative pressure can explain commitment to the TPNW. Statistical analyses show that regional normative pressure significantly increases the likelihood of commitment. Further analyses, using qualitative comparative analysis, indicate that this pressure is effective only toward states with previous nonproliferation commitments and where commitment to the TPNW does not entail a perceived weakening of national security. Thus, in the context of disarmament, normative pressure is trumped by security concerns.

KEYWORDS:

• Treaty on the Prohibition of Nuclear Weapons (TPNW)
• nuclear disarmament
• norms
• normative pressure
• civil society
• qualitative comparative analysis (QCA)

Acknowledgments

The author would like to thank the following people for their comments on previous drafts: Paul Beaumont, Målfrid Braut-Hegghammer, Anne Funnemark, Henrik Stålhane Hiim, Eskil Jakobsen, Sverre Lodgaard, Olav Schram Stokke, and two anonymous reviewers.

Notes

1 Treaty on the Prohibition of Nuclear Weapons, July 7, 2017.

2 For background reading on the TPNW negotiations, see, for example, Rebecca Davis Gibbons, “The Humanitarian Turn in Nuclear Disarmament and the Treaty on the Prohibition of Nuclear Weapons,” Nonproliferation Review, Vol. 25, Nos. 1–2 (2018), pp. 11–36; William C. Potter, “Disarmament Diplomacy and the Nuclear Ban Treaty,” Survival, Vol. 59, No. 4 (2017), pp. 75–108; Nick Ritchie and Kjølv Egeland, “The Diplomacy of Resistance: Power, Hegemony and Nuclear Disarmament,” Global Change, Peace & Security, Vol. 30, No. 2 (2018), pp. 121–41.

3 Beatrice Fihn, “The Logic of Banning Nuclear Weapons,” Survival, Vol. 59, No. 1 (2017), pp. 43–50; Motoko Mekata, “How Transnational Civil Society Realized the Ban Treaty: An Interview with Beatrice Fihn,” Journal for Peace and Nuclear Disarmament, Vol. 1, No. 1 (2018), pp. 79–92; Jonathon Baron, Rebecca Davis Gibbons, and Stephen Herzog, “Japanese Public Opinion, Political Persuasion, and the Treaty on the Prohibition of Nuclear Weapons,” Journal for Peace and Nuclear Disarmament, Vol. 3, No. 2 (2020), pp. 299–309.

4 Jean-Baptiste Jeangene Vilmer, “The Forever-Emerging Norm of Banning Nuclear Weapons,” Journal of Strategic Studies, Vol. 45, No. 3 (2022), p. 21.

5 Brad Roberts, “Ban the Bomb? Or Bomb the Ban? Next Steps on the Ban Treaty,” European Leadership Network, March 2018, p. 9, <https://www.europeanleadershipnetwork.org/wp-content/uploads/2018/03/180322-Brad-Roberts-Ban-Treaty.pdf>. See also Michal Onderco, “Why Nuclear Weapon Ban Treaty Is Unlikely to Fulfil Its Promise,” Global Affairs, Vol. 3, Nos. 4–5 (2017), pp. 391–404.

6 Heather Williams, “Why a Nuclear Weapons Ban Is Unethical (for Now),” RUSI Journal, Vol. 161, No. 2 (2016), p. 45.

7 Martha Finnemore and Kathryn Sikkink, “International Norm Dynamics and Political Change,” International Organization, Vol. 54, No. 4 (1998), p. 891.

8 See, for example, Finnemore and Sikkink, “International Norm Dynamics”; Alexander Wendt, “Anarchy Is What States Make of It: The Social Construction of Power Politics,” International Organization, Vol. 46, No. 2 (1992), pp. 391–425; Carmen Wunderlich, “Theoretical Approaches in Norm Dynamics,” in Harald Müller and Carmen Wunderlich, eds., Theoretical Approaches in Norm Dynamics (Athens, GA: University of Georgia Press, 2013), pp. 20–47.

9 Finnemore and Sikkink, “International Norm Dynamics”; Margaret E. Keck and Kathryn Sikkink, “Transnational Advocacy Networks in International and Regional Politics,” International Social Science Journal, Vol. 51, No. 159 (1999), pp. 89–101.

10 See Oona A. Hathaway, “Why Do Countries Commit to Human Rights Treaties?” Journal of Conflict Resolution, Vol. 51, No. 4 (2007), pp. 588–621; Beth A. Simmons, “Why Commit? Explaining State Acceptance of International Human Rights Obligations,” unpublished manuscript, University of California at Berkeley, Department of Political Science, 2002, <https://wcfia.harvard.edu/publications/why-commit-explaining-state-acceptance-international-human-rights-obligations>; Jay Goodliffe and Darren G. Hawkins, “Explaining Commitment: States and the Convention against Torture,” Journal of Politics, Vol. 68, No. 2 (2006), pp. 358–71.

11 See Beth A. Simmons, “International Law and State Behavior: Commitment and Compliance in International Monetary Affairs,” American Political Science Review, Vol. 94, No. 4 (2000), pp. 819–35.

12 Mariana Budjeryn, “The Power of the NPT: International Norms and Ukraine’s Nuclear Disarmament,” Nonproliferation Review, Vol. 22, No. 2 (2015), pp. 203–37; Mariana Budjeryn, “The Power of the NPT: International Norms and Nuclear Disarmament of Belarus, Kazakhstan and Ukraine, 1990–1994,” PhD diss., Central European University, 2016; Maria Rost Rublee, Nonproliferation Norms: Why States Choose Nuclear Restraint (Athens, GA: University of Georgia Press, 2009).

13 Matthew Fuhrmann and Xiaojun Li, “Rethinking Ratification: Legalization and Nuclear Weapon Free Zone Treaties,” Social Science Research Network, August 14, 2009, <https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1452775>.

14 See, for example, Potter, “Disarmament Diplomacy”; Vilmer, “The Forever-Emerging Norm”; Tom Sauer and Mathias Reveraert, “The Potential Stigmatizing Effect of the Treaty on the Prohibition of Nuclear Weapons,” Nonproliferation Review, Vol. 25, Nos. 5–6 (2018), pp. 1–19; Fihn, “The Logic of Banning Nuclear Weapons.”

15 Harald Müller and Carmen Wunderlich, “Nuclear Disarmament without the Nuclear-Weapon States: The Nuclear Weapon Ban Treaty,” Daedalus, Vol. 149, No. 2 (2020), pp. 179–80; Fihn, “The Logic of Banning Nuclear Weapons,” pp. 47–48.

16 Beth A. Simmons (“International Law and State Behavior”) identifies two groups of states among which norms are likely to exist: all states in the global system, and states sharing the same geographical region. Both levels are analytically interesting; however, this article focuses on capturing the variation in regional normative pressure. See also Fuhrmann and Li, “Rethinking Ratification”; Hathaway, “Why Do Countries Commit”; Simmons, “Why Commit?”; Goodliffe and Hawkins, “Explaining Commitment.”

17 Fuhrmann and Li, “Rethinking Ratification.”

18 Nick Ritchie and Alexander Kmentt, “Universalising the TPNW: Challenges and Opportunities,” Journal for Peace and Nuclear Disarmament, Vol. 4, No. 1 (2021), pp. 77–84.

19 Finnemore and Sikkink, “International Norm Dynamics”; John Borrie, “Humanitarian Reframing of Nuclear Weapons and the Logic of a Ban,” International Affairs, Vol. 90, No. 3 (2014), pp. 625–46.

20 Daniel Rietiker, Humanization of Arms Control: Paving the Way for a World Free of Nuclear Weapons (New York: Routledge, 2018), pp. 81–86.

21 Rietiker, Humanization of Arms Control, p. 126.

22 International Campaign to Abolish Nuclear Weapons (ICAN), “Partner Organizations,” n.d., <https://www.icanw.org/partners>; Mekata, “How Transnational Civil Society Realized the Ban Treaty”; Jonathan L. Black-Branch, The Treaty on the Prohibition of Nuclear Weapons: Legal Challenges for Military Doctrines and Deterrence Policies (Cambridge, UK: Cambridge University Press, 2021), pp. 287–90. For discussions on norm entrepreneurs, see Finnemore and Sikkink, “International Norm Dynamics”; Maria Rost Rublee and Avner Cohen, “Nuclear Norms in Global Governance: A Progressive Research Agenda,” Contemporary Security Policy, Vol. 39, No. 3 (2018), pp. 317–40; Müller and Wunderlich, “Nuclear Disarmament,” p. 180.

23 Black-Branch, The Treaty on the Prohibition of Nuclear Weapons, pp. 287–8. For a recent discussion on Dutch attitudes toward joining the TPNW, see Michal Onderco, Michal Smetana, Sico van der Meer, and Tom W. Etienne, “When Do the Dutch Want to Join the Nuclear Ban Treaty? Findings of a Public Opinion Survey in the Netherlands,” Nonproliferation Review, Vol. 28, No. 1–3 (2021), pp. 149–63.

24 Baron, Gibbons, and Herzog, “Japanese Public Opinion.” A similar study shows that Americans to a greater extent could be persuaded to shift their opinion from supporting the TPNW. See Stephen Herzog, Jonathon Baron, and Rebecca Davis Gibbons, “Antinormative Messaging, Group Cues, and the Nuclear Ban Treaty,” Journal of Politics, Vol. 84, No. 1 (2022), pp. 591–96.

25 Mekata, “How Transnational Civil Society Realized the Ban Treaty,” p. 86.

26 Matthew Fuhrmann and Yonatan Lupu, “Do Arms Control Treaties Work? Assessing the Effectiveness of the Nuclear Nonproliferation Treaty,” International Studies Quarterly, Vol. 60 (2016), p. 532.

27 Black-Branch, The Treaty on the Prohibition of Nuclear Weapons, p. 268.

28 John J. Mearsheimer, “The False Promise of International Institutions,” International Security, Vol. 19, No. 3 (1994–95), pp. 9–14.

29 Kenneth N. Waltz, “Nuclear Myths and Political Realities,” American Political Science Review, Vol. 84, No. 3 (1990), pp. 731–45; Charles L. Glaser, Analyzing Strategic Nuclear Policy (Princeton, NJ: Princeton University Press, 1990), pp. 361–69.

30 Kenneth Waltz, “The Spread of Nuclear Weapons: More May Be Better,” Adelphi Papers, Vol. 21, No. 171 (1981), pp. 1–32; Nuno P. Monteiro, Theory of Unipolar Politics (Cambridge, UK: Cambridge University Press, 2014), p. 91.

31 Stephen Herzog, “After the Negotiations: Understanding Multilateral Nuclear Arms Control,” PhD diss., Yale University, 2021, pp. 17–24.

32 Fuhrmann and Li, “Rethinking Ratification,” p. 31.

33 Scott D. Sagan, “The Causes of Nuclear Weapons Proliferation,” Annual Review of Political Science, Vol. 14 (2011), p. 239.

34 Williams, “Why a Nuclear Weapons Ban Is Unethical”; Matthew Harries, “The Ban Treaty and the Future of US Extended Nuclear Deterrence Arrangements,” in Shatabhisha Shetty and Denitsa Raynova, eds., Breakthrough or Breakpoint? Global Perspectives on the Nuclear Ban Treaty (London: ELN, 2017), pp. 51–57.

35 Williams, “Why a Nuclear Weapons Ban Is Unethical”; Harries, “The Ban Treaty,” pp. 51–7.

36 The two permanent nonmember observer states in the UN General Assembly are the Holy See and Palestine.

37 See Charles C. Ragin, Redesigning Social Inquiry: Fuzzy Sets and Beyond (Chicago: University of Chicago Press, 2008), pp. 13–4; Carsten Q. Schneider and Claudius Wagemann, Set-Theoretic Methods for the Social Sciences: A Guide to Qualitative Comparative Analysis (Cambridge, UK: Cambridge University Press, 2012), p. 3.

38 This is usually done by using a scale from 0 to 2, where 0 indicates no action, 1 indicates signing, and 2 indicates ratifying. See Goodliffe and Hawkings, “Explaining Commitment”; Simmons, “International Law and State Behavior”; Simmons, “Why Commit?”; Hathaway, “Why Do Countries Commit.” For an interesting discussion on the differences between signature and ratification as different levels of commitment, see Herzog, “After the Negotiations,” pp. 28–61.

39 This article uses the term “ratification” for both ratification and accession, as they have the same legal effect.

40 Membership labels are adapted from Ragin, Redesigning Social Inquiry, p. 31.

41 The data on states’ commitment status was last updated on February 13, 2023.

42 Goodliffe and Hawkings, “Explaining Commitment,” p. 361.

43 Simmons, “Why Commit?” p. 18.

44 Simmons, “International Law and State Behavior.”

45 Goodliffe and Hawkings, “Explaining Commitment”; Simmons, “International Law and State Behavior”; Simmons, “Why Commit?”; Hathaway, “Why Do Countries Commit.”

46 The regions are East Asia and the Pacific, Europe and Central Asia, Latin America and Caribbean, Middle East and North Africa, North America, South Asia, and sub-Saharan Africa. World Bank, “Countries and Economies,” n.d., <https://data.worldbank.org/country>.

47 The regional groups (number of member states in parentheses) are Andean Community (5), Arab League (19), ASEAN Plus Three (13), Caribbean Community (13), Central American Integration System (8), Commonwealth of Independent States (10), Economic Community of Central African States (11), Economic Community of West African States (15), European Council (45), Intergovernmental Authority on Development (7), Pacific Islands Forum (17), Southern African Development Community (14), South Asian Association for Regional Cooperation (8), and Southern Common Market (6). Ten states are members of two or more organizations. They were placed in the normative group to which they were determined to be ideologically closest. Eight states have been placed in an organization where they are observers or unofficial members, or from which they have been suspended. Cuba, Iran, Israel, Mongolia, and North Korea have not been placed in any regional group, due to their lack of membership in any significant group or because it is difficult to argue that they belong to a group with a common set of regional norms. The United States has not been placed in any regional group due to its hegemonic status in recent decades.

48 Yonatan Lupu, “Why Do States Join Some Universal Treaties but Not Others? An Analysis of Treaty Commitment Preferences,” Journal of Conflict Resolution, Vol. 60, No. 7 (2016), p. 1242.

49 For states with full membership (1.0), a share of at least 0.80 of a state’s co-members signed the TPNW. For states that are more in than out (membership 0.67), this share is between 0.57 and 0.80. For states that are more out than in (membership 0.33), the share is between 0.20 and 0.57. For states with no membership (0.0) the share is less than 0.20. Cuba, Iran, Israel, Mongolia, North Korea, and the United States, which have not been placed in any regional group, have been assigned a value of 0.50, and are thus more out than in the set (membership 0.33).

50 The Cook Islands and Niue were the only states that acceded to the TPNW before its entry into force without prior signature.

51 See Finnemore and Sikkink, “International Norm Dynamics,” p. 901.

52 See note 49.

53 Simmons, “Why Commit?”; Hathaway, “Why Do Countries Commit.”

54 ICAN, “Partner Organizations.” Data collected late 2020.

55 Sauer and Reveraert, “The Potential Stigmatizing Effect,” p. 451; Roberts, Ban the Bomb?, p. 2. See also Mekata, “How Transnational Civil Society Realized the Ban Treaty,” p. 89.

56 ICAN, “Become a Partner,” n.d., <https://www.icanw.org/become_a_partner>.

57 These states are all within the African NWFZ.

58 This operationalization covers the nine nuclear-armed states and 35 non-nuclear-armed states with a security guarantee from a nuclear-armed state: NATO member states, Japan, South Korea, and Australia, which are covered by the United States; and member states of the CSTO, which are covered by Russia.

59 Ragin, Redesigning Social Inquiry, p. 44.

60 Olav Schram Stokke, Disaggregating International Regimes: A New Approach to Evaluation and Comparison (Cambridge, MA: MIT Press, 2012), p. 67.

61 Ragin, Redesigning Social Inquiry, p. 46.

62 Ragin, p. 133.

63 See Table A1.

64 Consistency threshold of 0.80 and frequency threshold of 10 are applied.

65 Schneider and Wagemann, Set-Theoretic Methods, p. 105.

66 Schneider and Wagemann, p. 105.

67 United Nations, “Conference to Negotiate Legally Binding Instrument Banning Nuclear Weapons Adopts Treaty by 122 Votes in Favour, 1 Against, 1 Abstention,” <https://www.un.org/press/en/2017/dc3723.doc.htm>.

68 Ragin, Redesigning Social Inquiry.

69 Schneider and Wagemann, Set-Theoretic Methods, pp. 167–68.

70 The conservative solution is also known as the “complex solution.” See Schneider and Wagemann, Set-Theoretic Methods, p. 175.

71 Schneider and Wagemann, p. 175; Ragin, Redesigning Social Inquiry, pp. 171–75.

72 The most parsimonious solution is given as Solution Formula 1.3: N → Commitment. This solution often rests on assumptions about logical remainders that contradict theoretical expectations, common sense, or both (see Schneider and Wagemann, Set-Theoretic Methods, p. 175; Ragin, Redesigning Social Inquiry, pp. 171–75). The most parsimonious solution is nevertheless important because it defines the extremes of how far an introduction of simplifying assumptions can go without conflicting with the empirical evidence.

73 In the operationalization of “regional normative pressure,” Singapore is placed in the group ASEAN Plus Three, which also includes China, Japan, and South Korea. Singapore’s membership score in the set is more in than out (0.67). However, this may be an understatement of the real regional normative pressure that Singapore has experienced.

74 Gaukhar Mukhatzhanova, “The Nuclear Weapons Prohibition Treaty: Negotiations and Beyond,” Arms Control Today, Vol. 47, No. 7 (2017), pp. 14–16. See also Mely Caballero-Anthony and Julius Cesar Trajano, “Examining Southeast Asia's Diplomacy on Nuclear Disarmament and Nuclear Security: Shared Norms and a Regional Agenda,” Asian Journal of Peacebuilding, Vol. 10, No. 2 (2022), p. 10.

75 ICAN, “Singapore,” n.d., <https://www.icanw.org/singapore>.

76 Southeast Asian Nuclear-Weapon-Free Zone Treaty, December 15, 1995, Article 7.

77 Mukhatzhanova, “The Nuclear Weapons Prohibition Treaty,” pp. 14–16; Stuart Casey-Maslen, “The Nuclear Weapons Prohibition Treaty: Interpreting the Ban on Assisting and Encouraging,” Arms Control Today, Vol. 48, No. 8 (2018), p. 11; Alyn Ware, “The Ban Treaty, Transit and National Implementation: Drawing on the Aotearoa-New Zealand Experience,” Aotearoa Lawyers for Peace, June 27, 2017, <http://www.unfoldzero.org/wp-content/uploads/The-ban-treaty-transit-and-national-implementation-revised-final.pdf>.

78 William Tow, “U.S.-Southeast Asia Relations in the Age of the Rebalance,” in Malcolm Cook and Daljit Singh, eds., Southeast Asian Affairs 2016 (Singapore: ISEAS–Yusof Ishak Institute, 2016), pp. 35–55.

79 ICAN, “Argentina,” n.d., <https://www.icanw.org/argentina>.

80 Statement by Argentina to the UN General Assembly, September 26, 2019, <http://statements.unmeetings.org/media2/21998556/argentina.pdf>.

81 Reaching Critical Will (@RCW) “Argentina abstained on L.6 on #TPNW because it hasn’t yet signed. Participated in negotiations of #nuclearban and is continuing its analysis of the Treaty,” Twitter, November 4, 2020, 4.54 p.m., <https://twitter.com/RCW_/status/1324017147434147840?s=20>.

82 The share is 85 percent. World Public Opinion, “World Publics on Eliminating All Nuclear Weapons,” December 9, 2008, <https://worldpublicopinion.net/wp-content/uploads/2017/12/WSI_NucElim_Dec08_quaire.pdf>.

83 The other members of Mercosur are Brazil, Paraguay, Uruguay, and Suriname. Venezuela is suspended from Mercosur but is here treated as a member. The other non-signatory state to the TPNW in Mercosur is Suriname.

84 As quoted in Mekata, “How Transnational Civil Society Realized the Ban Treaty,” p. 86.

85 Carsten O. Schneider and Claudius Wagemann, “Standards of Good Practice in Qualitative Comparative Analysis (QCA) and Fuzzy-Sets,” Comparative Sociology, Vol. 9, No. 3 (2010), pp. 12–13.

86 Kim Sass Mikkelsen, “Negative Case Selection: Justifications and Consequences for Set-Theoretic MMR,” Sociological Methods & Research, Vol. 46, No. 4 (2017), p. 739; Olav Schram Stokke, “Qualitative Comparative Analysis, Shaming, and International Regime Effectiveness,” Journal of Business Research, Vol. 60, No. 5 (2007), pp. 509–10.

87 See Table A2.

88 Frequency threshold of 3 is chosen in order to include one configuration that is represented by three empirically interesting states that did not commit to the TPNW. These states are China, Japan, and South Korea, all of which have the following combination of conditions: N∗C∗z∗S.

89 The pairwise comparison has been done in the following manner: n∗C∗z∗S and n∗c∗z∗S reduced to n∗z∗S; n∗C∗z∗S and N∗C∗z∗S reduced to C∗z∗S.

90 The easy counterfactual is N∗c∗z∗S.

91 The values for this median case are regional normative pressure (0.33), civil society (1), NWFZ treaty commitment (1), and perceived weakening of national security (0).

92 See Mekata, “How Transnational Civil Society Realized the Ban Treaty.”

93 See Herzog, “After the Negotiations”; Sagan, “The Causes of Nuclear Weapons Proliferation.”

94 Harries, “The Ban Treaty,” p. 51.

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Espen Mathy

Espen Mathy works as a research fellow at the Norwegian Institute of International Affairs (NUPI), which he joined in September 2021. Prior to that, he completed internships at the Vienna Center for Disarmament and Non-Proliferation and the Vienna office of the United Nations Office for Disarmament Affairs. He has also worked as a policy fellow at the Norwegian Radiation and Nuclear Safety Authority. In 2013, he served as a trainee at the Royal Norwegian Embassy in Ankara. He holds a bachelor’s degree in international studies and a master’s degree in political science, both from the University of Oslo. He wrote his thesis on normative pressure and disarmament treaties in 2019 at NUPI, where he also worked as a research assistant. His research interests include the influence of norms on disarmament treaties and developments relating to the TPNW and other multilateral nonproliferation regimes.