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 Environmental Protection Agency (EPA) initially defined "source" to cover essentially any significant change or addition to a 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, avoiding any net change.

Natural Resources Defense Council, an environmentalist advocacy group, challenged the legality of the EPA's new definition.

[4] Forty years later, in June 2024, the Supreme Court overruled Chevron in Loper Bright Enterprises v. Raimondo,[5] on the grounds that it conflicts with the Administrative Procedure Act.

[3] At first, the EPA interpreted the word "source" in the new law to cover nearly any significant addition or change at a factory or plant.

[3][11] In 1981, after Ronald Reagan became President, the EPA changed its interpretation of the word "source" in the law to mean only an entire plant or factory, not an individual building or machine.

[3] The EPA's new interpretation allowed companies to make industrial decisions more freely as long as the total impact of their plants or factories on air pollution did not increase.

[3] In late 1981, the environmentalist advocacy group Natural Resources Defense Council (NRDC) filed a petition for review in the U.S. Court of Appeals for the District of Columbia Circuit challenging the legality of the EPA's new interpretation.

In an opinion written by U.S. circuit judge (and future Supreme Court justice) Ruth Bader Ginsburg, the D.C.

[14] The power of an administrative agency to administer a congressionally created program necessarily requires the formulation of policy and the making of rules to fill any gap left, implicitly or explicitly, by Congress.

At step two, the Chevron doctrine requires the court to evaluate whether the interpretation of the law that the executive agency proposes is "reasonable" or "permissible".

Several of the EPA's rulings for emissions regulations, as well as the Federal Communications Commission's stance on net neutrality have been based on cases decided on Chevron deference.

[23] The majority in Christensen v. Harris County (2000) suggested that Chevron deference should apply to formal agency documents which have the force of law while Skidmore should apply to less formal agency documents in an attempt to draw a bright line for the question of "force of law" under Chevron step zero.

In King v. Burwell (2015), the Supreme Court has suggested that Chevron deference may be inappropriate in regulatory actions of "deep economic and political significance",[24] hinting at the possibility of substantially limiting, or even eliminating, the doctrine.

[25] West Virginia v. EPA, 597 U.S. 697 (2022), established the first explicit use of the major questions doctrine by the Supreme Court,[26] which is seen to further weaken Chevron deference.

Under the major questions doctrine, rules and decisions made by executive branch agencies that are not explicitly defined by their Congressional mandate and may incur a significant economic or political cost raise major questions of the agency's authority, and thus can be deemed unlawful.

Roberts wrote in the majority of West Virginia, "[O]ur precedent teaches that there are extraordinary cases ... in which the history and the breadth of authority that the agency has asserted and the economic and political significance of that assertion provide a reason to hesitate before concluding that Congress meant to confer such authority.

"[27] Within the context of West Virginia, the major questions doctrine was applied to rule-making by the EPA to require existing power plants to implement "outside the fence" measures, beyond the scope of the power plant, to reduce emissions, as implementing these measures was considered costly.

The major questions doctrine was further evoked in Biden v. Nebraska, 600 U.S. ___ (2023), which determined that the Department of Education did not have the authority to cancel hundreds of billions of dollars in federal student loans under the HEROES Act.

[31] Some professors have suggested that the implications for medicine and public health as a result of overturning Chevron will be uncertainty and instability for agencies and industries, inviting legal challenges to any and all FDA, EPA and Centers for Medicare & Medicaid Services (CMS) determinations.

[32] The United States House of Representatives in the 115th Congress passed a bill on January 11, 2017, called the "Regulatory Accountability Act of 2017", which, if made into law, would change the doctrine of Chevron deference.

[38]: 1877 In Chevron U.S.A. Inc. v. Natural Resources Defense Council Inc., we established a test for reviewing "an agency's construction of the statute which it administers".

If that doesn't qualify as an unconstitutional revision of a judicial declaration of the law by a political branch, I confess I begin to wonder whether we've forgotten what might.

In April 2018, the state's governor Doug Ducey signed HB 2238 into law, which states in relevant part,[41] In a proceeding brought by or against the regulated party, the court shall decide all questions of law, including the interpretation of a constitutional or statutory provision or a rule adopted by an agency, without deference to any previous determination that may have been made on the question by the agency.The bill explicitly exempts health care appeals and actions of agencies created by the state's Corporation Commission.

[46] This article incorporates public domain material from judicial opinions or other documents created by the federal judiciary of the United States.