Not indicted, and yet they do care – Why EU governments file observations to cases before the ECJ

The European Court of Justice (ECJ) has been described not only as Europe’s constitutional court, but also as a politico-legal arena. Inter-institutional dynamics and conflicts between the branches of power manifest here. In this context, third-party interventions in court procedures deserve additional attention. It is mainly member state (MS) governments who act as third parties in ECJ cases by filing ‘observation’ letters in preliminary reference procedures (PRP). Recent research shows that number and preference of MS observations indeed have an effect on ECJ rulings. Third-party involvement evidently makes a difference at court. However, little is known about the factors that make governments participate as third parties. Building on theory and empirical insight on amicus curiae participation before the US Supreme Court this Paper asks which factors explain why and when EU MSs file observations in PRP. Should it only be the legal importance of a case which is decisive or do MSs care about court cases due to political reasons? The statistical analysis builds on two datasets. One covers all PRP referred by national courts between 1997 and 2008, including all submitted observations. It is matched with data that provides insight into political positions of MS governments and the political salience of issues that were controversial among MSs during the legislative process. The matched data allows a logistic regression of several hundred country-cases. It is shown that it is not only legal importance of a case but also sincere political positions which drive third-party involvement at court. MSs care about PRP because of their political salience. A major contribution is the differentiation and operationalization of legal importance and political salience of a court case.