States often violate international agreements, both accidentally and intentionally. To process complaints efficiently, states can create formal, pretrial procedures in which governments can negotiate with litigants before a case ever goes to court. If disputes are resolved during pretrial negotiations, it can be very difficult to tell what has happened. Are governments coming into compliance? If so, are they only doing so when they have accidentally committed a violation or even when they are intentionally resisting? Or are challenges simply being dropped? This paper presents a formal model to address these questions. We develop our theory in the context of the European Union (EU). To test our model, we collect a new dataset of over 13,000 Commission infringement cases against EU member states (2003–2013). Our results suggest that accidental and intentional noncompliance both occur, but that intentional noncompliance is more common in the EU. We find that the Commission is an effective, if imperfect, monitor and enforcer of international law. The Commission can correct intentional noncompliance, but not always. It strategically drops cases that it believes it is unlikely to win.

The European Union legal system is one of the most complex and sophisticated in the world. This article models the Acquis Communautaire (i.e. the corpus of European Union law) as a network and introduces the Evolution of European Union Law data set, which tracks connections between European Union primary law, European Union secondary law, European Union case law, national case law that applies European Union law, and national law that implements European Union law. It is the largest, most comprehensive data set on European Union law to date. It covers the entire history of the European Union , contains over 365,000 documents, and records over 900,000 connections between them. Legislative and judicial scholars can use this data set to study legislative override of the Court of Justice of the European Union, the implementation of European Union law, and other important topics. As an illustration, I use the data set to provide empirical evidence consistent with legislative override.

The Court of Justice of the European Union (CJEU) uses a chamber system to more efficiently decide cases. To what extent, and under what conditions, does the CJEU’s chamber system undermine the consistency of the Court’s application of EU law? This paper contributes to the literature on the internal organization of collegial courts by presenting a computational formal model that predicts (a) that hearing cases in smaller chambers undermines the consistency of the Court’s application of EU law and (b) that the magnitude of this effect is larger when judges’ preferences are more heterogeneous and smaller when plaintiffs strategically bring cases. Based on these findings, I use machine learning and empirical data on CJEU judgments in infringement cases to estimate the degree to which we should expect the chamber system to undermine the consistency of the CJEU’s application of EU law in practice.

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