Judicial Independence is a crucial aspect of the rule of law and the concept of separation of powers. It gives judges considerable leeway in interpreting and thereby modifying the constitution. In this paper, the role of the European Court of Justice (ECJ) as an actor in the strategic game played between the other actors on the European level as well as actors on the nation-state level (the respective governments, but also national courts, corporate actors and individuals) is inquired into. After describing the changes of the ECJs competence that have occurred since 1953, an attempt at explaining them is undertaken. It is shown that the ECJ has been able to bring about implicit constitutional change because its members are constrained less stringently than most supreme court judges on the nationstate level. It is furthermore shown that lower court judges have incentives to cooperate with the ECJ sometimes to the detriment of national supreme court judges.
