Multilevel polities do not typically facilitate secession, so why did the European Union adopt Article 50? Revisiting formative debates from the 2003 Convention on the Future of Europe, we combine archival research with an original dataset of delegate debates over two levels: the existence and procedural operation of an exit article. This reveals essential new detail on the genealogy of Article 50. We locate this institutional innovation within a Rokkanian–Hirschmanian theoretical framework which treats exit closure as necessary for loyalty and resilience. Further refining this ‘polity’ perspective, we find many participants showed awareness of the potentially disruptive implications of an exit article. Yet, given extant tensions around ‘ever closer union’, a Eurocentric procedural design prevailed as a safety valve, granting EU authorities default control over any exit process. This European logic of ‘controlled opening' offers a potential blueprint for other integrating compound polities and international organizations facing backlashes from member states.
