The Policy Impact of the Court of Justice of the European Union

This Chapter focuses on the policy impact of the judgments of the Court of Justice of the European Union (the Court). We define policy impact as the ability of the Court to produce change in the political domain. We analyze this impact across two different dimensions: horizontal and vertical. The horizontal dimension looks at the impact of the Court's rulings on European Union policies, that is, to what extent the judgments of the Court impact the policy output of the European Union legislator. The vertical dimension focuses on the impact of the Court's judgments on Member States' legal orders. We understand this broadly, as encompassing change as showing through in legislation, case law, policies, and administrative decisions. The Chapter systematically reviews the existing literature on policy impact across the vertical and horizontal dimensions to systematize existing knowledge and identify lacunas, shortcomings and challenges in the study of the Court's policy impact. We analyze the state of the art both in the legal and political science literatures. We find some stark disagreement as per the extent to which the Court impacts policy outcomes at the European Union level. Along the vertical dimension, the impact of the Court's rulings is generally accepted, but research mostly relies on qualitative studies and hence results greatly vary. Taking stock of the existing literature, with its strengths and weaknesses, in the last part of the Chapter we propose to think anew about how to empirically research the policy impact of the Court's judgments. This involves, on the one hand, rethinking some of the current dogmas and assumptions in the field. On the other hand, we argue that new empirical strategies need to be developed for a better study of the policy impact of the Court. To this end, we suggest several concrete elements that could push forward the empirical study of impact, and discuss the different limitations of our proposed approach (in particular, the unavailability of data) and how these could be overcome. We conclude with a reflection on how the empirical research on this field can not only enlarge our knowledge of the real impact of the Court's judgments, but also bridge and nuance some of the divergent views in legal and political science studies.