Voluntary codes of conduct for firms and private standards-setting bodies are growing in number and are increasingly gaining recognition and public status by states and intergovernmental organizations. This has led to a growth in what some have labeled as “mixed” regimes of a hybrid nature, whereby both states and private authorities are heavily involved in the creation and maintenance of international principles, norms, rules, and decisionmaking procedures. In such hybrid regimes, the boundary between public and private spheres is blurred. 1 In the environmental realm, the ISO 14000 series of environmental management standards recently adopted by the International Organization for Standardization (ISO) is illustrative of a hybrid private-public regime. These standards, intended to help firms take environmental considerations into account in all aspects of their operations by establishing an environmental management system (EMS) and other operation guidelines, were recently adopted by the membership of the ISO as official international standards. Though strictly voluntary for firms, the ISO 14000 standards are extremely important, as their impact goes beyond private industry. States are placing great hope in voluntary industry efforts to help improve environmental quality. 2 The ISO 14000 standards in particular are being adopted by standards-setting bodies in some states, either whole scale or in part, as national EMS standards. Moreover, these standards are now recognized by the World Trade Organization (WTO) as legitimate public standards and guidelines and in effect create an international ceiling for EMSs. 3 Industry has also been very supportive of the. ISO 14000 standards, as it hopes that adherence to them may preempt, or at least soften, present and future state-determined environmental regulations. 4