Current environmental problems trouble classical hierarchical state regulation approaches. Modern regulations, like the EC Water Framework Directive, tackle these problems by mandating states to warrant a certain status of the environment, i. e. in this case achieving a good status of waters. Focusing on the directive and the notion of “responsibility”, our paper analyzes modern approaches to state regulation. In order to live up to their “guarantor responsibility”, the states cannot rely on their state sovereignty alone but depend on voluntary initiatives of nongovernmental actors. Governance instruments, like negotiated environmental agreements or participation, can bring about such non-hierarchical forms of co-operation, but prove to be ambiguous. On the one hand, they might strengthen the state assertiveness and, on the other, weaken it because the states are at the mercy of third-party co-operation. Surprisingly, this co-operation does not lead to a withdrawal of the state: on the contrary, it necessitates a strengthening of governmental capacities.