Table of Contents: I. Introduction. – II. European law aspects of post-Brexit EU-UK cooperation. – II.1. Legal institutional possibilities and obstacles. – II.2. The withdrawal agreement. – II.3. Third country participation in CFSP. – III. International law aspects of post-Brexit EU-UK cooperation. – III.1. Existing and new CFSP/CSDP agreements. – III.2. International responsibilities and dispute settlement. – IV. Conclusion.

Abstract: Despite the ambition of the United Kingdom that Brexit should not lead to a complete de-tachment from the European Union’s foreign, security and defence policy – and, on the contrary, should lead to a new partnership – a post-Brexit cooperation on CFSP and CSDP matters raises a number of questions under both EU and international law. The present Article points to a number of restrictions in both EU primary and secondary law to allow the UK to maintain its participation in the key decision-making organs. At the same time, it assesses possibilities based on existing practices for third States to participate in EU external action.

Keywords: Brexit – foreign policy – CFSP – CSDP – EU – United Kingdom.

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European Papers, Vol. 4, 2019, No 2, pp. 427-445
ISSN 2499-8249 - doi: 10.15166/2499-8249/317

* Professor of International and European Law and Governance, University of Twente and Centre for the Law of EU External Relations (CLEER), ramses.wessel@utwente.nl. This Article was written during a visiting professorship at LUISS Guido Carli in Rome and finished thanks to the hospitality of Studio Legale Cannizzaro & Partners in Rome. Credits are due to Richard Haringsma, Eduard Hoek and Mika-el Waelen for their valuable work on this topic in their master theses for the European Studies programme at the University of Twente. These theses are accessible at www.essay.utwente.nl.