<p>The European Court of Justice (ECJ) has long been recognized as a major engine behind the European integration project for its role in passing judgments expanding the powers and scope of the European Community, while member states have consistently reacted negatively to judgments limiting their sovereignty or granting the Community new powers. It is this interplay between the Court and member state interests that cause the ECJ to pose a threat to the future of integration. Using a combined framework of neofunctionalism and rational choice new institutionalism, six landmark cases and the events surrounding them are studied, revealing the motivations behind the Court’s and member states’ actions. From the analysis of these cases is created a set of criteria which can be used to predict when the ECJ will make an activist decision broadening the powers of the Community at the expense of the member states as well as when, and how, member states will respond negatively.</p>

The European Court of Justice (ECJ) has long been recognized as a major engine behind the European integration project for its role in passing judgments expanding the powers and scope of the European Community, while member states have consistently reacted negatively to judgments limiting their sovereignty or granting the Community new powers. It is this interplay between the Court and member state interests that cause the ECJ to pose a threat to the future of integration. Using a combined framework of neofunctionalism and rational choice new institutionalism, six landmark cases and the events surrounding them are studied, revealing the motivations behind the Court’s and member states’ actions. From the analysis of these cases is created a set of criteria which can be used to predict when the ECJ will make an activist decision broadening the powers of the Community at the expense of the member states as well as when, and how, member states will respond negatively.