Differentiated participation, uniform procedures: EU agencies in direct policy implementation

European Union (EU) institutions have become increasingly involved in direct policy implementation in the member states, creating a new domain of differentiation in EU governance. What brings about such differentiation, and how does it vary across policy fields? Drawing on theories of differentiated integration, this article argues that differentiated implementation occurs at the intersection of postfunctional obstacles (politicisation) and functional pressures for joint implementation (interdependence). There are two identified dimensions of direct implementation, a territorial one referring to states' participation in such activities, and a procedural one capturing the degree of uniformity in the guidelines for organising implementation. The resulting typology is applied to direct implementation activities (DIAs) conducted by EU agencies alongside national authorities. The qualitative analysis reveals that differentiated participation is a stable feature of DIAs in politicised fields, and although there is a tendency to create more uniform procedures over time and across policy fields, higher uniformity prevails under symmetric interdependence.