What drives contemporary European polity formation?

What drives contemporary European polity formation? Kelemen and McNamara’s (2022) bellicist reading of the “unbalanced” and “incomplete” institutional development of the EU reinvigorated the debate on European state building by suggesting that European-level stateness will occur only in case the Union faces an existential military threat. In this paper, we test bellicist and alternative logics of European political development. We start from the assumption of the EU as a primarily “regulatory polity” (Majone 1996) and follow a Rokkanian understanding of polity formation as a combination of external boundary control and closure (Schimmelfennig 2021). We leverage a novel dataset of EU boundary configurations across 48 functional domains over 45 years. We show that, where the EU has developed increased levels of closure and control, it did so primarily to overcome the deficits inherent in its foundational regulatory template. From the 1980s through the early 2000s, the EU reacted to the scale and democratic deficits of Continental market-making by increasing legislative and judicial control, with concurrent debordering decreasing external closure. The capacity deficits laid bare by the increasing complexity in the Continental market and the crises of the 2010s then led the EU to gradually complement legislative and judicial with enhanced executive control. Finally, the security deficits of the permeable and fuzzy external boundaries of the regulatory polity, exposed by the string of security crises engulfing the European continent and its vicinity, heralded a movement toward increased external closure in the 2010s and early 2020s. In contrast to bellicist expectations, however, this rebordering dynamic has not resulted in increases in external boundary control. European polity formation, our analysis demonstrates, has become more balanced and complete than the bellicist reading suggests and, crucially, it reacts primarily to deficits and driving forces other than military threats.