Why EU Institutions Litigate Against Each Other: Material Interests, Institutional Logic or Politics?

Legal mobilization has been studied mostly in national settings, if explored in the EU multilevel system the focus rests mostly with national level actors complaining against the EU level or the interpretation of EU rules by national actors. However, mobilization also takes place at the supranational level and can run horizontally between EU institutions. This is the case where EU institutions question actions of other EU institutions in their application of EU law. Studying such horizontal annulment actions the paper describes the internal processes inside Commission, Council and European Parliament leading to the decision to launch an annulment action, litigant constellations and success rates. On this basis it explores three distinct hypothesis what motivates EU institutions to choose litigation over other strategies: a material/policy interest, an institutional logic or politics. Empirically it studies processes across policy areas, with a focus on those areas that are quantitatively most important in horizontal annulment actions: foreign policy, staff regulation, environment and energy as well as justice and home affairs. Methodologically the paper combines insights from a data base covering all annulment conflicts running horizontally between the EU institutions from 1957 to 2016 and cases study analysis based on insights from interviews with officials working in the EU institutions conducted in June 2016. It is part of a broader, multiannual project that studies litigation via annulment actions in the EU multilevel system.