We asked our senior fellow Brian Gray, a retired environmental law professor, to help us understand the implications of the US Supreme Court’s recent decision in Loper Bright Enterprises v. Raimondi, which overruled the “Chevron doctrine.”

Let’s start with a basic question: what was the Chevron doctrine?

The Chevron doctrine stems from the Supreme Court’s 1984 decision in Chevron v. Natural Resources Defense Council. The decision basically stated that if federal legislation is ambiguous or leaves an administrative gap, the courts must defer to the regulatory agency’s interpretation if the interpretation is reasonable. Notably, Chevron required the courts to defer to an agency’s reasonable interpretation of the statute, even if a court—left to its own devices—would interpret it differently.

So why did the Supreme Court abolish Chevron doctrine 40 years after creating it?

The court majority concluded that this type of judicial deference is inconsistent with another statute, which states that a reviewing court “shall decide all relevant questions of law.” In his opinion, Chief Justice Roberts also described how Chevron doctrine had proved to be unworkable and unpredictable.

I think the court overruled Chevron because, over time, the more conservative justices concluded that federal agencies had expanded their regulatory powers well beyond those delegated by Congress through an accretion of “reasonable” interpretations of the statutes that they administer.

What changes do you expect to emerge after the Supreme Court’s decision?

I’m concerned that future decisions will pay less attention to both the scientific realities that underlie our environmental laws and the agency expertise that enables these laws to function in the real world.

Regulatory statutes—especially those in the environmental and public health fields—are immensely complex and leave many important interpretative questions to the agencies. Resolving these questions frequently requires scientific and technical expertise that judges simply don’t possess. And these decisions have ripple effects: the interpretation of one statutory term often has implications for how an agency administers its regulatory programs overall.

Even in the best of political settings, amending legislation like the Clean Air Act and the Clean Water Act is a major undertaking that occurs only once every twenty years or so. The Chevron doctrine allowed the agencies administering these statutes to keep pace with changing conditions and new scientific understanding.

What are the likely consequences of the demise of Chevron doctrine?

I think the courts will now interpret statutes in a more mechanical manner, looking primarily to the putative “plain meaning” of the statutory text. A good recent example is the Supreme Court’s highly publicized 2023 decision in Sackett v. EPA, which rejected the EPA’s and the Army Corps of Engineers’ interpretation of the term “waters of the United States.”

The agencies decided that this term includes discharges into any waterway (including intermittent streams and hydrologically connected wetlands) that would “significantly affect the chemical, physical, and biological integrity” of adjacent or downstream navigable waters. They based their interpretation on scientific analyses of the hydrologic links between non-navigable and navigable bodies of water and the risks that discharges into the former pose to public health, fisheries, flood management, and other beneficial uses in the latter.

The Supreme Court rejected this interpretation. Instead, the Sackett majority relied on dictionary definitions of the relevant statutory text, and it limited agencies’ jurisdiction to continuously flowing tributary streams and wetlands that are physically adjacent to a navigable river or lake. This decision ignored the hydrologic realities on which the agencies’ interpretation was based, and it is likely to create a significant regulatory gap in many western states where non-perennial streams and wetlands predominate.

What are likely consequences of the Loper decision for California water policy?

I believe that the effects of Loper will be relatively muted. Most aspects of California water management and regulation are governed by state law, and the California courts have generally deferred to state agency interpretations of statutes governing water rights, water quality, protection of fish and wildlife, and management of wetlands and intermittent streams. In fact, the California Supreme Court has held that judicial deference is heightened when the statutory text is “technical, obscure, complex, open-ended, or entwined with issues of fact, policy, and discretion” and the agency has “expertise and technical knowledge” over the subject.

The California courts also have recognized that, in implementing and enforcing these laws, the State Water Resources Control Board has broad authority to make policy judgments that balance the myriad competing public interests. That said, the Loper decision will affect the interpretation of federal laws such as the Endangered Species Act that also significantly influence California water policy. There will be more to come!