The mantra of “take back control” has become a staple of eurosceptics across the European Union. At the centre of the slogan’s message is a call to arms against the (perceived) challenge that EU membership represents for national sovereignty. In this paper, we theorise that supranational decisions taken by the European Court of Justice can increase ‘polity scepticism’ - increased opposition to the EU and decreased satisfaction with national democracy – by cueing citizens regarding the effects of EU integration on the perception of diluted sovereignty. Empirically, we leverage quasi-experimental evidence to support our theory, establishing that ECJ rulings have a significant causal effect on euroscepticism and dissatisfaction with democracy. The implications of our findings suggest that EU institutions seeking to ensure compliance with the rule of law and EU norms should proceed with caution. Interventionist action may backfire by increasing scrutiny of the EU’s legitimacy and undermining polity support.