This FWO project aims to understand the balance of powers between the main European institutional actors in context of legislative decision-making in the Area of Freedom, Security and Justice (AFSJ). First, it investigates what changes legislative acts undergo during the legislative process from the text proposed by the European Commission to the final version published in the Official Journal of the European Union and which policy ideas, defined as policy provisions contained in the law, end up in the adopted document. Second, it accounts for the mechanisms and causal factors behind the influence of certain institutional actors and ideas on the development of legislation adopted in the AFSJ field. To do so the project relies on an application prototype of data mining and data processing, which allows a large-N systematic approach to track, visualize and analyze all legislative activity in AFSJ between May 1999 and December 2016. By tracing who ‘wins’ in the ‘legislative battle’, the project does not only fill an important gap in the literature on the AFSJ decision-making dominated by small-N and qualitative studies, but it also fuels the ongoing theoretical debates on the influence of institutional actors and on the impact of ideas on the European legislative outcomes. Moreover, the application of data mining and data processing techniques to legal text can contribute to test the efficiency of different computational modeling methods.