Exactly how should an excellent regulator intervene in the affairs of regulated organizations to ensure compliance (and arguably over-compliance) and facilitate enforcement? That question motivates this paper, which is about the “intervention strategies” used for compliance and enforcement rather than about “resource allocation.” In the absence of any consensus as to what criteria an excellent intervention strategy should satisfy, I accept the convention that the principal criteria for choosing an intervention strategy should be effectiveness and efficiency. In the majority of cases, the effectiveness of any intervention in reaching a social or economic target (i.e., reducing social or economic harm) and its efficiency (i.e., doing so at least cost) will be the primary concerns of policymakers. Legitimacy or political acceptability, including positive public perceptions of the regulator, is also important. As will become apparent, though, regulators inevitably confront trade-offs that must be made between all of these criteria.