Collective Security Through Alliance Security: Examining the Legal Framing of European Collective Security Components After Brexit

Following the Brexit decision, both the European Union and the United Kingdom expressed the importance of safeguarding collective security in a post-Brexit world. In 2017, European Chief Negotiator Michel Barnier stated that as Europe embarked on an ‘unprecedented effort to establish a Defence and Security Union’ without the UK, the European community would have to ‘draw the appropriate legal and operational conclusions’. With latent assurances that the UK was ‘leaving the EU, not leaving Europe’, former UK Prime Minister Theresa May stated in 2018 that ‘[w]e must do whatever is most practical and pragmatic in ensuring our collective security’. This paper examines the analytical framing of collective security for the UK and the EU in the wake of Brexit. The question of the UK’s future role within the European security landscape begins with a more fundamental question about the legal doctrine of collective security under international law. This analysis begins with addressing the concept of ‘collective security’, which is a dynamic doctrine that draws from an interworking lattice of rules, power dynamics and normative assumptions. Who are the credible organs of the internationalised collective security architecture? What are the terms for participation in this architecture? And how will the UK and the EU establish legal arrangements within this configuration? These questions are being raised within the context of existing shifts in the legality of use of force and multilateralism. Increasingly, Member States enact ‘collective measures’ without explicit Security Council authorisation, undermining the centrality of the UN Security Council. The veto power of the Permanent members continues to raise doubts about the substantive equality between powerful and weak States. The traditional configuration of collective security working mainly to address State actors seems ill-suited to a reality where ‘internal and external security become more and more entwined’. Regional arrangements and defensive alliances such as the Economic Community of West African States Monitoring Group (ECOMOG) and the North Atlantic Treaty Organisation (NATO) increasingly invoke the language of collective security goals as legal grounds for peace-keeping and interventionist operations. However, are these claims well substantiated within the confines of existing doctrine? And is there significant tension between the universal goals of collective security and the fundamentally exclusionary construction of alliance security? This paper interrogates the basic assumptions, changing landscape, and conceptual tensions of the collective security doctrine and what these shifts reveal about the UK’s place in the future European Security identity.