The evolution of European Union law: A new data set on the Acquis Communautaire

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 (1951–2015), 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.