National Audubon Society v. Superior Court (Mono Lake decision)

The Mono Lake decision expanded the Public Trust Doctrine in California and held that agencies and courts were required to consider and protect public trust resources and ecosystem effects when diverting water for consumptive use. More broadly, it was a critical case in expanding the Public Trust Doctrine beyond only concerning navigable waters and rights to commerce, navigation, and fishing.

Background
In the 1940's the City of Los Angeles obtained rights to divert water from several streams fielding Mono Lake in the Sierra Nevada mountains. Over time, the water diversions lowered the lake level and threatened unique ecosystems. In 1979, environmental groups filed suit to enjoin the diversions on the grounds of violating the Public Trust Doctrine. The case made its way to the California Supreme Court.

Relevant Laws and Principles

 * Public Trust Doctrine

Ruling
The California Supreme Court ruled in favor of the environmental groups, finding that the public trust doctrine applied to the diversions from Mono Lake’s tributary streams, and that the doctrine protected the fish and wildlife in those streams and in Mono Lake itself. The Court charged state agencies and courts with considering public trust values when making decisions impacting public trust resources.

Takeaways
The opinion expanded the scope of the Public Trust Doctrine in California beyond submerged lands to water rights administration and beyond navigable waters to all tributaries affecting navigable waters. The case was an important step in expanding the scope of the Public Trust Doctrine more broadly. Numerous U.S. states have since expanded the doctrine. The greatest impact has been internationally however, where the Public Trust Doctrine has come to be applied to a wide range of natural resources and even codified into the constitutions of various countries.