Abstract The Lisbon Treaty has introduced new categories of acts that cut across the familiar typology of instruments provided for in Article 288 TFEU. The three main innovations are "legislative acts", "regulatory acts" and "delegated acts". The article critically analyses these legal concepts in the light of the institutional practice recently developed under the EU Treaties. It includes the first generation of "special" legislative acts adopted by the Council, the landmark rulings of the General Court in Inuit and Microban, the Comitology Regulation of February 2011 and the "Common Understanding on delegated acts" concluded in March 2011. The theme common to the three studies is the progressive parliamentarization of the Union. The Lisbon Treaty's re-arrangements in the system of legal acts are part of the difficult process of reworking the EU's constitutional settlement in view of a powerful European Parliament and the demand to translate this new political reality into the operations of the legal order. For instance, Parliament's persistent objection to the previous regime of supervising the Commission's law-making powers through a system of committees was the driving force behind the new rules of Articles 290 and 291 TFEU. In the case of "regulatory acts", however, the parliamentarization of the Union has provoked a dysfunctional spillover into EU procedural law.