We describe a simple mechanism for achieving two goals: (1) to encourage firms to take environmentally friendly action, and (2) to make environmental protection impervious to political change. We assert that there is wide evidence now that firms adopting an environmental management system (EMS) like ISO 14001 improve their environmental performance. This is because ISO 14001's third-party audits reduce the chance firms will fully fail to comply with regulations, and the EMS procedure reduces the chances firms will be in noncompliance due to ignorance. Our mechanism is intended to harness the power of EMS systems within firms, while reducing the chances that political change will nullify our solution. We argue that to achieve these goals, governments should make firms' participation in public procurement programs contingent on their adoption of an EMS such as ISO 14001.