External drivers of EU differentiated cooperation: How change in the nuclear nonproliferation regime affects member states alignment

ABSTRACT

Since its establishment, the Common Foreign and Security Policy (CFSP) has strived to increase convergence among EU member states. Yet, convergence remains elusive and scholars have started to explain the emergence of differentiated cooperation resulting from multiple internal EU crises. We posit that the convergence in the EU member states with respect to nuclear weapons has been fundamentally altered by the humanitarian turn to nuclear disarmament. This has led to a crystallization of differentiated subgroups among the member states, whose membership coincides with that of informal groupings active in the broader nuclear nonproliferation regime. Combining quantitative data on resolution sponsorship at the Non-Proliferation Treaty review process and voting at the UN General Assembly, we show that significant change in the international nuclear nonproliferation regime led to differentiated cooperation within the CFSP, resulting in two cohesive subgroups of member states.

KEYWORDS:

• Differentiated cooperation
• CFSP
• differentiation
• NPT
• nuclear weapons
• TPNW

Acknowledgements

An earlier version of this paper was presented at the authors’ workshop at the EUI in Florence in October 2021. We thank the organizers of the workshop and the editors of this special issue, Maria Giulia Amadio Viceré and Monika Sus, as well as Benjamin Martill and Stephanie Hofmann, for helpful comments. We are also grateful to the CSP editors and two outstanding reviewers for their helpful suggestions which greatly benefited this article. We thank Marin Lucic and Femke Verburg for diligent research assistance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 The UK was an EU member from 1973 to 2020.

2 Finland and Sweden did not apply for NATO membership until 2022. Since our data cover the period until 2020 (for UNGA) and 2015 (for NPT) only, these countries are not considered as NATO aspirants for the purposes of this study.

3 Given that different metrics can be used to indicate which countries are supporters of the Humanitarian Initiative, we chose the co-sponsorship of the statement delivered by Austria at the 2015 RevCon (Kurz, 2015) as an accurate indicator of support, given that the project had achieved maturity at that juncture.

4 The data shows one-off variation in Greece’s voting in 2010, which was mainly due to some erroneous votes, and which is systematically irrelevant.

5 Some EU members joined various nonproliferation informal arrangements – such as the Nuclear Suppliers Group or the Zangger Committee – only at the time of EU accession. The EU regularly calls on others to join such regimes (EEAS, 2018).

6 Council Conclusions omit any mention to the TPNW, referring instead to the “humanitarian impact” of nuclear weapons and to their “very severe consequences.”

Additional information

Funding

This project was supported from Charles University Research Centre program under Grant UNCE/HUM/028 (Faculty of Social Sciences / Peace Research Center Prague).

Notes on contributors

Michal Onderco

Michal Onderco is Professor of International Relations at Erasmus University Rotterdam and affiliate at Peace Research Center Prague. He studies international security, with focus on nuclear politics and on domestic politics of foreign policy. He authored Networked Nonproliferation (Stanford UP, 2021) and Iran’s Nuclear Program and the Global South (Palgrave, 2016), as well as papers which appeared in International Studies Quarterly, European Union Politics, Journal of Common Market Studies, Contemporary Security Policy, European Journal of Political Research, Cooperation & Conflict, The Nonproliferation Review (and elsewhere). In 2018–2019, he was a Junior Faculty Fellow at Stanford University’s Center for International Security and Cooperation.

Clara Portela

Clara Portela is Konrad Adenauer Visiting Scholar at Carleton University’s Centre for European Studies in Ottawa, Canada, and a professor at University of Valencia in Spain. She previously served as a professor at Singapore Management University and as a research fellow with the European Union Institute for Security Studies (EUISS) in Paris, where she dealt with arms control and disarmament issues. She holds a PhD from the European University Institute in Florence and an MA from the Free University of Berlin. She co-edited the volume “The EU and the Non-Proliferation of Nuclear Weapons" (2015), among various publications on EU foreign policy. She is the recipient of the THESEUS Award for Promising Research on European Integration.