The book offers explanations for the striking variation in the outcomes of European integration crises. It analyzes eight major cases over the entire integration process, starting from the early 1950s and lasting until very recently. All cases went beyond a single policy field or member state but affected key features, principles, and objectives of European integration. As such, they qualify as “constitutional crises”. My cases comprise the crisis of the European Defence Community (1952-54); the empty chair crisis (1965-66); the oil crisis (1973-74); the budgetary rebate crisis...