One of the institutional innovations provided for in the Lisbon Treaty is the European Citizens’ Initiative (ECI), which aims to engage European citizens with the European project, help mobilise civil society and strengthen pan-European debate on European policies. But what happens if a citizens’ proposal is deemed inadmissible by the European Commission? CEPS Researcher Piotr Kaczy?ski considers this question in a new Commentary and makes suggestions for an appropriate response by the European Commission and other institutions.