When the United Kingdom and Denmark were granted controversial opt-outs from the Maastricht Treaty, researchers argued that they would lead to a ‘Europe in bits and pieces' and that differentiated integration serve to destabilise the Union and freeze out member states. Nevertheless, the details of what happens when a member state opts out have remarkably remained uncharted territory over the years. At first sight, national protocols might appear to undermine the solidarity and cohesiveness of the EU; however, this thesis demonstrates that the diplomatic repair work of the opt-outers contribute to upholding a doxa of ‘ever closer union among the peoples of Europe'.

Empirically, the thesis provides the first extensive study of the diplomatic practices of the two champions of opting out - the UK and Denmark - when they handle their most important opt-outs from the Economic Monetary Union and Justice and Home Affairs. Theoretically, the study offers a political sociology of European integration, which is seen as driven by politico-administrative struggling for capital in quasi-autonomous fields. This approach can be used more generally by EU and IR scholars to understand social dynamics of inclusion and exclusion.

Drawing on the work of Pierre Bourdieu and Erving Goffman, the thesis demonstrates that an opt-out may become a stigma, i.e. a discrediting mark on national representatives. Building on 123 in-depth interviews and archival material, the thesis unravels how normative discipline leads to the pursuit of stigma management strategies by British and Danish representatives as they attempt to fight marginalisation. These findings challenge existing assessments of the impact of opt-outs and differentiated integration and demonstrate why it is necessary for institutional entrepreneurs to consider the everyday social setting of international and regional governance.