Brexit and the Emergence of a Transnational European Community of Practice: From Grassroots Mobilisations to Supranational Political Opportunity Structures in the Struggle for Citizens' Rights

Abstract Brexit ignited an unprecedented sense of shared European identity and belonging, catalysing pro‐EU social movements among EU nationals in the United Kingdom and amongst British citizens residing in the EU and leading to the formation of a transnational European community of practice. This mobilisation coalesced around grassroots organisations whose claim‐making strategy was rooted in the institution of EU citizenship, which also grounded their legitimacy. Drawing on a relational approach to diasporic and transnational social movements, mixed methods empirical research including the findings of an online survey of mobile citizens ( n = 1919), archival and documentary analysis, expert interviews and policy analysis, the article analyses the significance of supranational political opportunity structures to the emergence of a transnational European community of practice during Brexit and the formation of an alliance between two of the primary grassroots organisations advocating for citizens' rights – the3million and British in Europe.