Chapter 3 reconstructs the functioning of the European legislative process in practice. To this end, it systematizes the main normative instruments that steer and discipline the behavior of European political actors and civil servants, including the (rather bare) Treaty provisions, the relevant interinstitutional agreements, the European Parliament’s Rules of Procedure, and the provisions set out in internal documents, especially administrative circulars. This chapter posits that administrative circulars are important for institutional interactions, as they contribute to regularizing the conduct of political actors (regulative component), creating normative expectations (normative component), and generating values, beliefs, and assumptions that actors internalize and accept as part of their “repertoire of unquestioned routines and habits” (cultural-cognitive component). As far as trilogues are concerned, all these provisions testify to the existence of a norms-based, institutionalized environment, congenial to legal analysis.