Constitutional and Supreme Courts play an important role in our understanding of comparative politics. With their right of constitutional review they are able to block legislation passed by parliament. Even more, their rulings usually allow them to define a framework of possible policies for future governments. Thus, on the level of political systems courts are usually understood as veto players (Tsebelis 2002, Volcansek 2000) or elements of consensus democracy (Lijphart 1984, 1999).
This perceived role stands in stark contrast to our knowledge about the mechanisms determining the influence of courts in political systems. We have precious little systemic knowledge about composition rules, access routes of political actors to the courts and isolation of the court from political pressure in a comparative perspective in Europe.
However, these Aspects determine the position of the courts in the political system (Composition), the activity of the courts (Access/Adjudication) and the likelihood of strategic behavior by the judges (Independence). All in all, these Aspects define the institutional rules governing the interaction between the courts and the actors of the political system. In order to understand the role of courts on the level of political systems, we systematically need to analyze these rules and furthermore the changes of these rules over time.
Therefore this study analyses two research questions. First, how can we measure the institutional characteristics of courts with the power of judicial review? Second, can we observe changes of institutional rules over time?
We construct three different indices - based on the different aspects of independence, access and composition - to measure the degree of judicial power, which we define as the ability to make independent decisions. Our dataset contains all high courts - constitutional and supreme courts - with the ability to review legislative acts in the member states of the European Union. To observe institutional stability and change, we measure the characteristics at three time slots for each of the courts: 1995, 2005, 2015. To obtain the data we code the constitutional rules and the legislation concerning the courts for each time slot. To measure the degree of institutional variation of courts we use two strategies. First, a theory driven index construction and an analysis the institutional variations and changes on the three dimensions of judicial power. Second, we run a cluster analysis to define subgroups of countries.
Our shows, that there is a broad variance within the institutional design of courts. Furthermore, we see that the courts in Eastern Europe have more executive-centered composition rules, very broad level of adjudication and lower levels of independence. The analysis of the changes within the institutional rules show strong changes for the adjudication dimension, which leads to an empowerment of the courts with the exemptions of Poland an Hungary. Finally, the results of the cluster analysis shows several subgroups of countries.
