Many nations have developed policies and enforced legal approaches for addressing the needs of species at risk of extinction. Generally, however, conservation reliance is not acknowledged legally and is therefore ignored. Increasingly, legal approaches reflect the importance of (1) values in addition to hunting and fishing, (2) wildlife as a shared resource, (3) intrinsic rather than instrumental value, (4) helping species to become self-sustaining, and (5) long-term support for imperiled species. The International Union for the Conservation of Naturehas provided an international standard for recognizing species status. In the United States, the Endangered Species Act and National Environmental Policy Act provide a legal framework for species conservation that has been effective (although these acts have also spawned many legal challenges that have consumed the time and resources of stakeholders). The effectiveness of imperiled species laws depends on funding that can vary, leading to varying implementation and enforcement. Conservation reliance is seldom addressed explicitly. Responsibility for implementation may be spread across national, state or province, and more local entities.

Solar geoengineering is presently being researched through indoor work and outdoor experiments without potential transboundary impacts. Existing national and subnational legislation and common law govern such activities, including for their environmental risks, and is an essential component of the existing governance framework within which solar geoengineering is developing. To offer a case study, this chapter reviews applicable American law. The United States was chosen because its environmental legal regime is among the most elaborate and influential, and because solar geoengineering research is presently moving forward most rapidly there. The text considers three major pieces of federal environmental legislation: the Clean Air Act, the National Environmental Policy Act, and the Endangered Species Act. Liability for harm, which is found in the common law of torts, is briefly introduced. Thereafter, the chapter describes relevant laws regarding weather modification and marine pollution, as well as a federal geoengineering bill. A salient question throughout this concerns the extraterritorial application of US law.