Tanja Börzel argues that the effect of Europeanization on the politics and institutions of the EU's member states depends on the degree of conflict between European and domestic norms and rules. This book examines the relationship between the central state and regions in Germany and Spain, showing how Europeanization has served to weaken the powers of the regions. In both countries, the regions were forced to cooperate more closely with the centre, but the institutional impact in the two countries has been strikingly different. In Germany the existing cooperative Federal system was reinforced, but in Spain the traditional competitive relationship between the levels of government could not continue. Europeanization has led to a significant change in the pattern of Spanish politics, turning rivalry into cooperation. This book thus presents an important analysis of the impact of Europeanization on domestic politics, and on the relationship between states and regions in particular.