Subsidiarity ex-ante and ex-post: From the Early Warning System to the European Court of Justice

The Lisbon Treaty aimed to strengthen the enforcement of the subsidiarity principle in the European Union (EU). Ex-ante, national parliaments were given a role as watchdogs of subsidiarity under the Early Warning System (EWS). Ex-post, the Lisbon protocol on subsidiarity and proportionality explicitly allows for judicial review of adopted legislation by the European Court of Justice (ECJ). Ten years after Lisbon, this article is the first to analyze and evaluate whether there is a connection between ex-ante and ex-post subsidiarity review. As a central principle regulating the distribution of competences between the EU and the member states, subsidiarity is important to study. Quantitatively, we analyze and provide a two-way classification of member states based on their use of the EWS and ECJ subsidiarity cases, for the period 2010-2020. Qualitatively, we analyze the opinions of the Advocate General (AG) in subsidiarity cases to assess whether the complainant or the AG refer back to subsidiarity arguments made ex-ante in the EWS. We find that limited reference is made to it, and that the AGs tend to take a procedural approach to ex-post subsidiarity review, reaffirming broad discretion for the EU institutions. Referring to the existence of the EWS, the Court seems of the view that subsidiarity is mainly a political principle. In conclusion, despite the spirit of the Lisbon Treaty, the link between ex-ante and ex-post subsidiarity review seems weak. We speculate that new generations of AGs may take a less procedural view of subsidiarity, strengthening the enforcement of the principle.