The article investigates two questions, first why the EP has played different roles in different policies and second which type of governance regimes have accommodated those different roles. Based on the historical-institutionalist approach, the article argues that the EU has come to structure, since the 1992 Maastricht Treaty, different constitutional logics for dealing with the regulatory policies of the single market and the policies entered the EU agenda and traditionally close to core state powers. Based on comparative legislatures’ approach, the article thus shows that, although the post-Lisbon EP has proceeded towards its ‘normalization’, the latter however has assumed neither parliamentary nor congressional features, given the quasi...