The Major Questions Doctrine Can’t Save EPA’s Big Climate Repeal

The Trump administration attacked a linchpin of federal climate policy last week: The Environmental Protection Agency formally repealed the landmark endangerment finding and all greenhouse gas emission standards for cars and trucks.

The endangerment finding is a 2009 determination by the EPA that greenhouse gas emissions from new cars and trucks cause or contribute to dangerous air pollution. This scientific judgment triggered an obligation for the EPA to regulate such pollution under the Clean Air Act. It has undergirded nearly 15 years of vehicle regulations issued under administrations of both parties, including the first-term Trump administration.

But the EPA now argues that it has no legal authority to regulate greenhouse gas emissions from cars and trucks because the relevant provision of the Clean Air Act authorizes regulation of only local and regional air pollution that directly harms human health.

This argument is a legal lemon. In a 2007 decision, Massachusetts v. EPA, the US Supreme Court rejected similar arguments and confirmed that greenhouse gas emissions are unambiguously “air pollutants” subject to the EPA’s endangerment assessment.

The EPA argues that the major questions doctrine, or MQD, has upset this established landscape. But as we explain below, and in our recent report, the EPA’s arguments misunderstand the MQD, ignore Supreme Court precedent, and contradict principles of stare decisis.

EPA’s regulation of greenhouse gases from motor vehicles doesn’t trigger the MQD. The MQD requires “clear congressional authorization” when an agency acts in ways that are unheralded, transformative of the agency’s regulatory authority, and economically and politically significant. The Supreme Court has stressed that only “extraordinary cases” trigger the MQD.

In the repeal, the EPA suggests the MQD is triggered because the endangerment finding required the agency to broaden its statutory authority “to encompass global climate change concerns.”

But the EPA overlooks a lengthy history of Clean Air Act regulation of those pollutants which, like greenhouse gases, cause indirect and non-exposure-based effects on human welfare. This history includes regulation to prevent effects such as eutrophication, damage to the ozone layer, and even climate change.

It further ignores that Congress explicitly directed the Clean Air Act to reach pollutants that cause “effects on...weather, visibility, and climate,” and legislative history corroborates this intention. Regulating greenhouse gas emissions is neither unheralded nor transformative and thus fails two of the required MQD prongs.

The EPA also incorrectly asserts that the MQD applies because the regulation would force the market toward cleaner vehicle technologies—a normal result of pollution regulation that was considered when the Clean Air Act was designed. As the EPA itself previously explained, it’s applying a decades-old approach to vehicle regulation that doesn’t trigger the MQD.

The Supreme Court already rejected the essential components of EPA’s MQD argument. The court in Massachusetts squarely addressed and rejected the substance of the MQD arguments raised in the repeal. Though the court didn’t explicitly refer to the “major questions doctrine” by name, it addressed materially the same argument when it distinguished FDA v. Brown & Williamson, one of the MQD’s foundational precedents.

When the EPA announced the MQD in West Virginia v. EPA, the court cited Brown & Williamson repeatedly, and recognized it as one of “a series of significant cases” solidifying the MQD.

Fatally for the EPA, the court in Massachusetts considered Brown & Williamson and found nothing unprecedented or transformative about the EPA regulating motor vehicle greenhouse gas emissions. The court noted that the EPA itself had previously affirmed that it had the power to regulate these emissions and that doing so would be within the scope of its Clean Air Act authority. Seven years later, in Utility Air Regulatory Group v. EPA, the court reaffirmed this conclusion.

In Massachusetts, the court also recognized that Congress provided the clear authorization necessary, finding that the relevant Clean Air Act provision “clear[ly]” and “unambiguous[ly]” applied to greenhouse gases. In sum, the court rejected functionally the same arguments from the repeal that the EPA issued last week.

EPA’s arguments violate statutory stare decisis. Even if the court hadn’t already rejected the EPA’s MQD arguments, statutory stare decisis forestalls its arguments. As the Supreme Court has explained, “considerations of stare decisis weigh heavily in the area of statutory construction” because “Congress is free to change this Court’s interpretation of its legislation.”

As the court clarified in its 2024 ruling in Loper Bright Enterprises v. Raimondo, this principle remains true even after a change in the court’s interpretive methodology. So even assuming that West Virginia marked a meaningful change in “interpretive methodology,” (which it doesn’t, as explained above), the holding of Massachusetts is due the “enhanced force” of statutory stare decisis.

For almost two decades, Congress has done nothing to undermine the court’s interpretation that greenhouse gas emissions are air pollutants subject to regulation—and in several instances, Congress has affirmed that interpretation.

In short, the MQD can’t help the EPA relitigate an argument that it lost in Massachusetts. Nor do other more recent decisions such as Loper Bright come to the EPA’s rescue, as we have noted previously.

State attorneys general and environmental groups have already pledged to challenge the repeal in court. Time will tell if the rule survives judicial review, but the MQD shouldn’t save it.

This article does not necessarily reflect the opinion of Bloomberg Industry Group, Inc., the publisher of Bloomberg Law, Bloomberg Tax, and Bloomberg Government, or its owners.

Author Information

Dena Adler is a senior attorney and Kate Welty is a legal fellow at NYU School of Law’s Institute for Policy Integrity, a non-partisan think tank dedicated to improving the quality of governmental decision-making.

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