Regional parliaments were for a long time neglected in EU policy-making. The main way for them to try to influence EU legislation was to try to control their regional executive, which - in many cases - had only limited influence itself. The failed Draft Constitutional Treaty and later the Treaty of Lisbon changed the situation by allowing regional parliaments to participate in the new Early Warning System (EWS). The introduction of the EWS provided regional parliaments with new opportunities to engage with EU legislative proposals, and is seen to have the ability to empower regional parliaments in a number of ways. This study analyses to what extent regional parliaments make use of the EWS in practice. On the basis of an analysis of the reasoned opinions of regional parliaments from four member states the chapter argues that the impact of regions on the parliamentarisation of the EU is still limited.