European defence: How can the EU best work with the UK and other non-EU states?

On April 29, 2025, a seminar at St Antony’s College, University of Oxford, brought together experts to examine how the European Union can best engage with the United Kingdom and other non-EU states in the context of evolving security and defence challenges. The panel featured Brendan Devlin, EU Visiting Fellow at St Antony’s College; Luigi Scazzieri, Senior Policy Analyst at the European Union Institute for Security Studies; and Armida van Rij, Senior Research Fellow at Chatham House. The discussion was chaired by Professor Timothy Garton Ash, Professor of European Studies at St Antony’s College. The speakers offered insights into the potential for a new European Defence Procurement Treaty, the implications for non-EU states such as the UK, and the broader geopolitical and institutional dynamics shaping European defence cooperation.

Brendan Devlin introduced the idea of a European Defence Procurement Treaty that would include both EU and non-EU countries. Drawing on the 2005 Energy Community Treaty as a precedent, he proposed a treaty framework that would operate under qualified majority voting, allowing it to function efficiently despite an expanded membership. He stressed the importance of ensuring “equivalence of esteem” for non-EU countries, in contrast to the EU’s traditional enlargement approach, which he described as a "take-it-or-leave-it" process that limits third countries’ influence. Devlin also argued for granting the treaty legal personality and rights, which would allow it to administer funds and engage in host government agreements. He proposed that participation should not be contingent on accepting the EU’s four fundamental freedoms, thereby offering flexibility for third-country involvement. Additionally, he suggested that the treaty include provisional application and sunset clauses to enable it to enter into force before full ratification and to allow it to expire automatically over time, avoiding the pitfalls of institutional permanence. He noted that EU directives—specifically Directives 2009/81/EC and 2009/43/EC—could serve as a legal foundation for this treaty, although he emphasised that real progress would require political initiative and a shared strategic outlook.Luigi Scazzieri placed the discussion in the broader context of European defence integration. He observed that despite growing cooperation between EU member states on capabilities and procurement, there is still no unified European defence market. The EU has taken on a more proactive role, particularly after Russia’s full-scale invasion of Ukraine, with the development of initiatives such as the European Defence Fund for 2021–2027 and mechanisms like Permanent Structured Cooperation. However, Scazzieri pointed out that non-EU partners, while involved in some operations, generally lack decision-making rights. He identified two main obstacles to deeper defence integration with third countries: protectionist tendencies aimed at safeguarding domestic defence industries and jobs, and security sensitivities, especially around export controls and intellectual property. He explained that most EU defence instruments are tied to the single market and industrial policy, and since they are often funded through the EU budget, they are inherently structured to differentiate between member states and external partners. This institutional asymmetry, he argued, continues to hinder the development of a pan-European defence market.

Scazzieri noted the distinction between special arrangements available to countries like Ukraine, which benefit from tailored funding, and a third category of states such as the UK, which face limited and conditional participation. Nonetheless, he stressed that the UK remains a uniquely positioned partner due to its regulatory and industrial alignment with the EU. In his view, a tailored approach grounded in political realism and gradualism is likely the most practical path forward for UK-EU defence cooperation.

Armida van Rij added a broader geopolitical perspective, highlighting several key forces driving the need for renewed UK-EU cooperation on defence. These include the consequences of Russia’s war against Ukraine, the possible return of Donald Trump and a revival of isolationist U.S. foreign policy, and a shifting global landscape involving strategic actors such as Iran, North Korea, China, and India. Van Rij raised concerns about the growing influence of far-right movements in Europe, some of which receive encouragement from U.S. actors, and warned that such trends could further destabilise long-term European cooperation. She also noted internal divisions within the EU on major foreign policy issues, especially regarding China and Ukraine.

Van Rij argued that any future strategy for UK-EU defence relations must include the development of institutional infrastructure that supports strategic autonomy and reduces overreliance on the United States. She underscored the importance of engaging the public in these discussions so that citizens understand why increased defence cooperation matters. Additionally, she called for better alignment between high-level strategic goals and the more politically sensitive policy areas such as trade and regulation, particularly in the wake of Brexit. In her view, defence should be the foundation—rather than the culmination—of a revitalised partnership between the UK and the EU.

During the Q&A session, audience members raised concerns about the practicality of establishing an entirely new institution and legal framework. Some suggested it might be more efficient to expand existing institutions such as the European Commission, the European Investment Bank, or the European Bank for Reconstruction and Development. In response, Devlin acknowledged that while those institutions could be extended, they do not serve for democratic purposes. The real barrier, he argued, is the absence of clear political direction from Brussels. Scazzieri added that even small, incremental steps in defence cooperation remain difficult to implement without strong support from EU member states.

Additional questions focused on the scope of the proposed treaty, with Devlin clarifying that although procurement would be the starting point, the treaty could be designed to expand over time, much like the Energy Community’s eventual move into investment. On the issue of EU-UK cooperation, Devlin acknowledged that while the defence internal market does not allow for selective participation, the UK could still play a meaningful role if it is prepared to adapt to the structural realities of the system. Van Rij and Scazzieri also addressed questions about the EU’s relationship with the United States. Both noted that the EU continues to rely heavily on U.S. defence technology, and any move toward strategic autonomy would involve difficult decisions and trade-offs.

The seminar concluded with a shared recognition that although legal and policy frameworks for broader European defence cooperation already exist, activating them will require political will, coherent strategy, and institutional flexibility. Non-EU countries like the UK remain essential to Europe’s defence architecture, but their participation will depend on navigating a complex mix of political, legal, and economic factors with care and pragmatism.

by Yangyang Zhao