Compliance is a ground that justifies obedience by an actor particularly when others comply. Non-compliance by important members creates a situation where complying states contribute to the production of a collective good but will be exploited by free-riders (Olson 1965, 29). Non-compliance by states which are important for international problem-solving can diminish the belief on the part of complying nations that they will be able to achieve their goals in an institution. It can undermine the regularity of social relations and cause an erosion of social order. Whether norms and rules deserve obedience depends not only on compliance by others. The character of norms and rules also determines whether compliance is justified. Environmental norms and rules deserve obedience if they give prospect of improvements in the environment and if they avoid that strongly asymmetrical outcomes will emerge. In the following, attention will first be paid to measuring the level of compliance by all members in the issue area. Measurements will also focus on the compliance behavior of important states. It will be clarified whether deepened penetration of states by regime policies increased compliance problems. In exploring the causal impact of regimes for observed levels of compliance, it will be assessed whether compliance resulted primarily from the operation of international regimes or has been caused by external factors. In presenting the empirical results collected for our dependent variable, the frequency distribution on ordinal scales which were developed for measuring the degree of compliance by members will be illustrated for all regime elements and for a sub-set of regime elements ending in 1998. In addition, a check for intercoder reliability will be carried out for data of our dependent variable. In addition, those events and actions will be explored that were necessary or significant for translating international commitments into domestic obligations in important member states. In a second step, it will be explored whether institutional mechanisms or nonstate actors contributed to compliance. A theoretical approach focusing on the institutional design as a factor that impacts on compliance leads us to expect that compliance is dependent on the existence of various institutional mechanisms. Since environmental governance systems frequently lack mechanisms which could be used to enforce regime rules in case of non-compliance, special attention will be given to exploring whether institutional mechanisms emerged which could influence the management of compliance problems. An approach which focuses on the role of non-state actors suggests that compliance problems will partly be diminished by the involvement of governments and stakeholders in transnational discourse about the necessity and rightness of policies. This approach leads us to expect that governments will be forced by environmental actors to explain

the causes for noncompliance to the public or be pressurized to change behavior accordingly. In addition, this approach leads us to expect that compliance by states is dependent on the service and expertise of non-state actors which they contribute in compliance mechanisms and on the willingness of affected economic groups to implement regime policies.