The research question addressed in this report is why the EU procedure for developing network codes for electricity was enacted in its particular form. Passed by the EU in 2009, European organisations partly outside of the formal EU structure were given a mandate to make rules that would apply across the EU. This was puzzling given the observed resistance on part of the member states to let go of national control over energy issues. Drawing on institutionalist perspectives, the analysis shows that the procedure would not have been passed without support from and compromise among the Commission, European Parliament and the member states in Council; that parts of the procedure imitated existing practices within related policy areas; that horizontal and vertical specialization within the nation-states along with a Commission actively promoting transnational cooperation changed the feedback mechanisms, which changed the direction of European energy market regulation; and finally, that the new actors played an active role vis-à-vis EU bodies as the latter were legislating on the procedure.