EDOARDOCROCI IEFE - Universita Bocconi, Milano, Italy Voluntary approaches in environmental policy represent a "third wave" of regulation in the environmental field. "Command and control" was the first wave. Its core is based on uniform emission standards, the respect of which needs to be enforced through extensive monitoring and severe sanctions. The expected cost of sanction for non-compliance, calculated as its amount multiplied for the probability to be caught, must be superior to the benefits of non-compliance, in order to let the sanction be effective. As the benefits of non-compliance...