According to German Federal President Gauck, the European Union is the "greatest political success story of our continent". Yet growing numbers of Europeans fear the uncontrollable powers of an emerging European superstate. Where should one draw the line at further steps toward the express treaty goal of an "ever closer union" in order to preserve sufficient autonomous policy-making powers of the member states as well as maintain public support for the EU? In its 2009 judgment on the constitutionality of the Treaty of Lisbon, the German Federal Constitutional Court drew up a list of competences which the German state could not transfer to the EU, comprising the core areas of criminal law and procedure, the internal and external use of force, public revenue and expenditure, the shaping of living conditions in a social state as well as culture. On that basis, the papers in this volume discuss the constitutional limits of European integration from different national perspectives.