International cooperation in general, and European integration in particular, requires that states translate their international commitments into domestic policy changes. Implementation of international agreements is vital. The author finds that the involvement of national parliaments in European integration does not hinder the integration process because it improves implementation records even while potentially slowing down negotiations. This process appears most clearly in the case of Denmark, where parliamentary involvement is intense and constant. Similarly, regional authorities can plague implementation efforts unless they are integrated into negotiation at an early stage. Thus, democratic accountability supports, rather than obstructs, effective integration.