Global governance research is aware that the proliferation of international institutions creates horizontal "interface conflicts" between sectoral spheres of international authority and therefore problems for cooperation among states. The question how relevant actors respond to such conflicts is, however, addressed only at the margin. Against that backdrop, this paper has two goals: First, to grasp conceptually and empirically the forms of handling interface conflicts that emerge from the interaction between sectoral spheres of international authority. Second, to explain under which conditions different forms of handling interface conflicts prevail. We conceive of the handling of an interface conflict as an interactive outcome emerging from the individual responses of different types of relevant actors to such a conflict. To identify interface conflicts of this type, we draw on the secretariats of those twelve international organizations (IOs) with the highest degree of authority according to a database developed at the WZB. Each of the selected cases is then studied and coded with respect to the responses of states, IGOs, and NGOs to interface conflicts, and with respect to the resulting interactive management of these conflicts. In sum, we shed light on how actors cope with the challenges "interface conflicts" pose for inter-state cooperation.
