Despite the growing literature on Brexit, specifically, and conflicts of sovereignty, more generally, there has been insufficient research on how the concept of sovereignty has been used in citizen campaigns and street protests across the United Kingdom – a form of ‘counter-democracy’ through which people attempted to oversee the post-referendum political process. Combining qualitative content analysis of campaign websites with a discourse-network analysis of media articles on Brexit protests, this article shows that claims to sovereignty were mobilised not only in conflicts between the United Kingdom and the European Union, but also in conflicts between different institutions within Britain itself. Both ‘Leavers’ and ‘Remainers’ appealed to popular and parliamentary sovereignty at different points in time, pragmatically adapting their framing according to changing circumstances but also as a result of a dynamic series of interactions with each other, including denying, keying and embracing their opponents’ frames. Crucially, conflicts around different institutionalisations of popular sovereignty did not demand system change, a rhetoric familiar from other protests of the 2010s such as Occupy Wall Street with its emphasis on ‘We are the 99%’. To the contrary, pro- and anti-Brexit mobilisations remained firmly focused on Brexit policy itself. They problematised the split between ‘Remainers’ and ‘Leavers’ within the United Kingdom, between 48% and 52%, and thus, on a deeper level, the tension between the political principle of popular sovereignty and the sociological reality of a split country. Finally, the more Leavers opposed Remainers, the more movements and parties on each of these two sides aligned. Politicians featured prominently in campaigns and as speakers at protest events, contributing to close cooperation between protesters and parties, and precluding anti-systemic discourses around popular sovereignty that would target parties and institutions altogether.