Abstract The Lisbon Treaty represented a rare opportunity to redesign parliamentary control of the European Commission's delegated powers. The new Treaty distinguishes between delegated and implementing acts and specifies that comitology rules must be decided by a co-decision regulation. This necessitated a reform of the comitology system, which was decided in December 2010 after protracted inter-institutional negotiations. This article asks why the new control system took its final form. The negotiations as a game of control positions are analyzed and the course of the negotiations is traced through documents and interviews. Support is found for the article's hypotheses, but it is also the case that events in some respects went further than expected.