According to the literature on parliamentary government, legislatures provide political parties with veto and amendment rights, which counterbalance executive power. This institutional feature is also said to help overcome ministerial “drift” within coalition governments. While this literature has focused on the situation of an unconstrained environment of parliamentary government, the European Union’s Member States continuously delegate policy competencies to Brussels, whose directives must in turn be transposed into national law to take effect. Because the minister in charge enjoys informational advantages and has the sole right to begin the process of implementing directives, he can completely control the agenda in this constrained environment. We evaluate the empirical implications of a ministerial gatekeeping model by investigating the (in)activities of 15 countries with respect to 2,756 EU directives adopted between December 1978 and November 2009. Our findings show that partisan ministerial approval is necessary to start the implementation process which conditions the counterbalancing response of parliaments. Accordingly, the delegation of policy competencies to the European Union changes the power relationship in parliamentary governments and increases the risk of partisan ministerial drift.