Testing Supranational and Intergovernmentalist Theories: Is the European Court of Justice a Mere Instrument in the Hands of Member States?

Scholars agree that the European Court of Justice (ECJ) is an essential actor in the processes of European integration. Interpreting the EU legislation, the Court has often changed dramatically the status quo in the European law at the dislike of some member states. The last two decades of research generated a solid theoretical base that clarifies the role of ECJ as an actual decision-maker. The two leading theories of integration, neofunctionalism and intergovernmentalism, generate opposite predictions on the driving forces of the ECJ ruling. Both theories present empirical evidence in supporting such predictions. However, previous studies either focus on a handful number of cases ruled by the ECJ or they allow heterogeneity among observations for not discriminating between precedents and subsequent cases of minor importance. In this paper I advance the argument that legal circumstances predetermine most of the political implications, such as the promotion of European integration, that the ECJ decisions possibly create. Thus, in the case of the ECJ, the two theories of integration do not necessarily contradict but are frequently complementary one to another. The validity of this central argument, as well as the verification of some existing hypotheses, require an improved test which accounts for these circumstances. I manually coded all cases brought in front of the Court since 1954. My original dataset includes crucial explanatory variables such as the judicial procedure, reference in the posterior case-law, composition of the Court, area of legislation, and data on the litigants. Empirical results strongly support my main argument.