Apparently affirming ideas of ‘every state for itself’, the Brexit vote puts models of constituent power in the EU under pressure. In particular, the UK referendum seems to undermine the notion of pouvoir constituant mixte, according to which the EU derives its democratic legitimacy from the citizens in two roles, namely as European and member state citizens. In this paper, I defend this idea against three objections. First, I address the analytical challenge of whether ‘split’ popular sovereignty can still be presented as a rational reconstruction of the EU constitutional order after the decision of one of the largest member states to withdraw from the EU. Second, I turn to the political challenge of whether the pouvoir constituant mixte with its supranational implications can be a promising candidate for a public narrative that allows citizens to recognize the value of EU in a time when many people seem to be concerned about losses of national self-determination. Third, I deal with the theoretical challenge of whether academic attempts to identify a founding authority of the EU represent a category mistake that may have contributed to the flawed idea – which was popular in the referendum campaign – that the UK could return to a (fictitious) status quo ante and re-activate an ‘original’ democratic agent that had lost its power in the course of European integration.
