After Brexit: How Externalities Shape Differentiated Disintegration in UK-EU Relations

The relations between the United Kingdom (UK) and the European Union (EU) after Brexit vary considerably across issue areas. In some issue-areas, such as migration, the UK is satisfied with mere withdrawal or even seeking rapprochement with the EU. In other issue areas, such as finance, post-Brexit contestation of the EU has further exacerbated, with the UK trying to undermine the EU’s policies from the outside. What explains this variation in cooperative or conflictual disintegration in the UK-EU relationship after Brexit? We argue that variation in the effects the EU exerts on non-members in different issue areas, and thus different patterns of dependence, strongly influences a leaving state’s choice of moderation or escalation of EU contestation after withdrawal. More specifically, we suggest that where the UK faces (no) negative externalities from EU policies after Brexit, it will further escalate (terminate) its contestation. We probe our argument with comparative case studies of the EU-UK relations after Brexit in the issue-areas of migration, fisheries, finance, trade, security, as well as culture and education. Our paper challenges post-functionalist approaches to differentiated disintegration, while refining bargaining power approaches to differentiated disintegration. Moreover, our paper yields implications for the politics of post-exit relationships between leavers and international organizations beyond the EU.