Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc.

Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837 (1984), was a landmark decision of the United States Supreme Court that set forth the legal test for when U.S. federal courts must defer to a government agency's interpretation of a law or statute. The decision articulated a doctrine known as "Chevron deference". Chevron deference consists of a two-part test that is deferential to government agencies: first, whether Congress has spoken directly to the precise issue at question, and second, "whether the agency's answer is based on a permissible construction of the statute."

The decision involved a legal challenge to a change in the U.S. government's interpretation of the word "source" in the Clean Air Act of 1963. The Act did not precisely define what constituted a "source" of air pollution. The Environmental Protection Agency (EPA) initially defined "source" to cover essentially any significant change or addition to a plant or factory. In 1981, the EPA changed its definition to mean only an entire plant or factory. This allowed companies to build new projects without going through the EPA's lengthy new review process if they simultaneously modified other parts of their plant to reduce emissions so that the overall change in the plant's emissions was zero. Natural Resources Defense Council, an environmentalist advocacy group, successfully challenged the legality of the EPA's new definition.

Chevron is one of the most important decisions in U.S. administrative law. It has been cited in thousands of cases since its issuance in 1984. Thirty-nine years later, in May 2023, the Supreme Court granted certiorari to reevaluate Chevron in Loper Bright Enterprises v. Raimondo, No. 22-451. A decision is expected in the first half of 2024.