Whereas individual Member State governments of the European Union occasionally complain about judgments of the European Court of Justice (ECJ), especially when those judgments curtail that State's policy autonomy in a sensitive domain, the collectivity of the Member State governments have agreed in each treaty revision so far to confirm and extend the far-reaching powers which the ECJ possesses for enforcing EU law. The explanation of the paradox can only be that, deep down, the Member States of the EU remain convinced that an effective ECJ with strong enforcement powers is one of the salient features of EU law which have stood the test of time and feel no inclination to clip the wings of the ECJ for fear that this would affect the effectiveness of the European integration process. Nevertheless, the grumblings about single judgments, or about the consistency and direction of the ECJ in particular policy fields, have never ceased and indeed have become more audible in recent years. This book - now available in paperback - deals with the perception that the ECJ quite often does not leave sufficient autonomy to the Member States in developing their own legal and policy choices in areas where European and national competences overlap.