Whose polity is the European Union? The predominant views present it either as a cosmopolitan order based on a political community of European citizens or as a demoi-cratic system deriving its legitimacy from citizens organized as peoples of member states. This paper defends a position that steers a middle course between these two approaches. According to the notion of pouvoir constituant mixte, the adequate conception of the EU’s constitutional subject is a combination of the community of European citizens on the one hand and the communities of state citizens on the other. While this idea seems intuitively plausible because it avoids the respective one-sidedness that characterizes the common approaches, its proponents have thus far only provided ‘anecdotal evidence’, such as references to article 10 (2) TEU. Starting from a Habermasian framework, this paper seeks to reconstruct the practice of EU constitutional politics in order to systematically justify the idea of a pouvoir constituant mixte and to explicate a number of principles for the legitimate exercise of constituent power on the European level.
