As part of the modern environmental movement of the 1970s, five states (Hawaii, Illinois, Massachusetts, Montana, and Pennsylvania) adopted constitutional amendments recognizing a right to a quality environment, a public trust for public natural resources, or both. Half a century later, there is a renewed interest in constitutional environmental rights, inspired in no small part by the failure of existing laws to adequately address the climate crisis. A sixth state (New York) recognized a constitutional right to a quality environment in 2021, and more than a dozen states are considering such amendments. Still, the great majority of environmental protection at the state level is accomplished by statutes and regulations. In that context, what specific value do constitutional provisions add to environmental and natural resources protection? This Article attempts to answer that question for U.S. states, based on judicial decisions in these six states. These provisions can contribute value in at least three ways, depending on how they are written and how courts interpret and apply them. First, constitutional environmental rights and public trusts limit governmental authority to act contrary to their provisions. They can be the basis for invalidating inconsistent statutes, regulations, and other government actions. They can be used in a variety of ways to improve access to the courts, and they have been used to broaden and deepen protection for public natural resources beyond the protection accorded under traditional public trust law. Second, they provide supportive authority for govern- mental efforts to protect the environment and natural resources. Third, they can provide the basis for legal actions against private parties.

Constitutional environmental rights and public trusts are not a silver bullet for all environmental problems. But they can add value to a state’s environmental and natural resources protection effort in a rich variety of ways.