This book revisits the Treaty of Lisbon's promise to further parliamentarize the EU's functioning by looking into the Treaty-law framework governing the delegation of legislative power in the EU. In this field, the Lisbon Treaty formally greatly strengthened the position of the European Parliament vis-à-vis both the European Commission and the Council. The book explores whether Parliament's formally reinforced role is reflected in the actual balance of powers in the area of delegated legislation and executive rule-making. It does so by assessing how both the law and practice of decision-making at the legislative level, looking at specific case studies, and the sub-legislative level, examining the scrutiny over delegated legislation, has crystallized in the ten years following the entry into force of the Lisbon Treaty. This rigorous study gives a fascinating insight into one of the most significant developments in European parliamentary law-making, which EU constitutional lawyers will find required reading.