The following is a comment submitted on behalf of The Institute for Energy Research on the Environmental Protection Agency Proposed Rule – Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards
Docket ID No. EPA-HQ-OAR-2025-0194-0093
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Comment submitted by:
Institute for Energy Research
1155 15th St NW Suite 500
Washington, DC 20005
Kenneth Stein, Policy Director
September 22, 2025
Assertions of regulatory power over greenhouse gases (GHGs) are enormous claims of regulatory power. GHGs are byproducts of all human activity. Human respiration itself emits GHGs. Claiming regulatory power over GHG emissions is a claim of regulatory power over all human activity. This sort of massive claim of authority is precisely the sort of major question that the Supreme Court in West Virginia v. EPA held can only be undertaken with a clear grant from Congress. Congress has made no such clear statement. In light of this, the Institute for Energy Research strongly supports the EPA’s proposal to rescind its endangerment finding for GHGs from tailpipe emissions. This action will return EPA to more clearly appropriate regulatory bounds. Should Congress in fact desire EPA to regulate GHGs in ways not already authorized, then it is incumbent on Congress to pass legislation to clearly give the authority to do so as well as establish the purpose and aims of such regulation.
Congress did not authorize GHGs to be covered by the Clean Air Act
“I think the Supreme Court came up with a very much erroneous decision on whether the Clean Air Act covers greenhouse gases. Like many of the members of this committee, I was present when we wrote that legislation and we thought it was clear enough that it did not.”
– Rep. John Dingell, former Chairman House Energy and Commerce Committee
(C-1) A look at the legislative history of GHG legislation shows clearly that Congress did not intend for the Clean Air Act (CAA) to cover GHG emissions. The CAA focused on the impacts of toxic compounds emitted into the air and the problem of visible pollution in the skies. Congress has repeatedly debated regulatory programs and actions on GHGs over the course of decades. This subsequent action indicates clearly that Congress did not and does not intent the CAA to cover GHGs.
To name just two examples, extensive debate occurred in 2010 on proposed cap and trade regulations for GHGs, but Congress declined to pass such legislation. Extensive consideration of GHG regulations and limits were part of the buildup to passage of the Inflation Reduction Act in 2022, but Congress declined to pass regulations on GHG beyond some provisions regarding methane emissions. Even those methane-related provisions have subsequently been repealed or weakened by Congress. Many more legislative proposals and amendments regarding GHGs have been proposed and debated, and yet regulation of most GHGs never passed Congress.
Congress has however passed some legislation authorizing regulation of specific GHGs. In addition to methane provisions mentioned above, Congress granted regulatory authority over hydrofluorocarbons (HFCs) in December 2020, and the Senate later ratified the Kigali Amendment to the Montreal Protocol, an agreement to phase out HFCs entirely. This history of legislative action makes clear that Congress has not clearly granted authority to regulate GHGs, with the exception of HFCs. Indeed, the fact that Congress has chosen to regulate some GHGs, while debating and choosing not to regulate other GHGs, should be taken as clear evidence that Congress has not authorized the regulation of most GHGs by EPA. This lack of action should be understood as deliberate inaction, Congress has chosen to leave most GHGs beyond federal regulation.
Not only has Congress not spoken clearly on regulation of most GHGs, conflicts with another statute passed by Congress strongly indicate that CAA regulation of GHGs, particularly CO2, is not authorized by Congress. The only means of reducing CO2 emissions from tailpipes is through fuel efficiency. But fuel efficiency is the subject of a separate congressionally mandated regulatory scheme, the Corporate Average Fuel Economy standards. This presents a conflict, since if Congress intended for CO2 to be regulated under CAA Section 202(a), as the endangerment finding presupposes, then Congress has passed two different regulatory mandates for CO2. The existence of CAFE standards is yet another indication that Congress did not intend for CAA Section 202(a) to apply to CO2 and other GHGs emissions from tailpipes. Instead of assuming that Congress passed two different conflicting statutes addressing the same issue, a more logical reading is that CAA Section 202(a) was meant to apply to toxic emissions that are addressable through fuel supply modifications or technological interventions like catalytic convertors.
The record of action (and inaction) by Congress is very clear. Congress has elected to regulate some GHGs, and Congress has debated and elected not to regulate other GHGs. EPA’s proposed rescission of its 2009 endangerment finding comports with this clear congressional intent. The endangerment finding was administrative overreach even at the time it occurred, and subsequent actions by Congress have only reinforced that the decision was beyond congressional intent.
EPA’s rescission recognizes the flawed logic in Massachusetts v. EPA
(C-24) The Supreme Court’s 2007 decision in Massachusetts v. EPA was a flawed reading of statute. As expressed in the quote from Rep. Dingell above, the majority decision went well beyond the intent of Congress in giving EPA the option of regulating GHGs under the CAA. The CAA was not designed to regulate GHGs, and subsequent efforts to regulate GHGs have made this obvious as regulatory efforts have been repeatedly struck down in the courts (e.g. Utility Air Regulatory Group v. EPA, 573 U.S. 302 (2014), West Virginia v. EPA 597 U.S. 697 (2022)).
Additionally, the expansive logic of Massachusetts v. EPA, assuming the broadest possible definitions of air pollutant and harm, has subsequently been contradicted by the holding of West Virginia v. EPA, which held that “major questions” (such the authority to regulate a byproduct of all human activity) must derive from a clear grant of authority from Congress. While Massachusetts v. EPA purported to consider major question implications, it only considered it in a perfunctory manner. In addition, in 2007 the major questions doctrine was a more vague analysis concept, easily dismissed by the goal-oriented majority. West Virginia v. EPA elevated major questions to controlling precedent. Thus the limited and inadequate consideration of major questions in Massachusetts v EPA is of great importance in the current proposed rule. If Massachusetts v. EPA were heard today, it would certainly be considered a major questions case, and thus would turn on the existence of a clear grant from Congress (or lack thereof, as discussed above). EPA is correct to take a narrower approach to defining pollutant and harm under the CAA. This proposed action is more in keeping with legal developments since 2007, especially West Virginia v. EPA.
An additional flaw in the logic of Massachusetts v. EPA, which this proposed rule correctly addresses, is that the term “pollutant” must have some particular meaning. It is unreasonable to be able to apply the label “pollutant” to any and all molecules emitted from a vehicle tailpipe. Despite Massachusetts v. EPA allowing for such a broad reading, EPA is correct to take a more limited and logical approach. As noted above, the most logical interpretation of the term pollutant in 202(a) is that it refers to the kinds of toxic pollutants that are directly harmful and are addressable with technological interventions like catalytic convertors. GHGs do not make sense within the definition of pollutant in the CAA as they do not cause direct harm to humans, nor do they contribute to direct harm. Water vapor is the most significant GHG, and it is emitted from vehicle tailpipes. And yet it would generally be agreed that regulating water vapor emissions would be an absurd outcome. If Congress intended 202(a) to regulate any and all molecules that exit a tailpipe, they could have used extremely broad language. By choosing to make “pollutants” the targets of regulation, EPA must assume that Congress intended that only some emissions should be covered by 202(a).
Attempting to shoehorn GHGs into 202(a) by positing that they “contribute” to harm also requires leaps of logic. All the posited harms from GHGs are indirect, on the theory that eventually accumulations lead to warmer temperatures which then cause some climate effects and those climate effects then impact humans. But possible indirect future impacts are far too tenuous to be considered as “harming human health” under the CAA definition. Indeed, according to the IPCC consensus, other than increased temperatures, no climate impacts from GHG accumulation have actually been observed to date. So EPA’s theory of regulating is effectively pre-crime, regulating GHGs in the belief that at some point in the future they will harm human health and welfare. Thus EPA’s proposed rule represents a far more reasonable reading of the statute. Instead of tying itself in knots attempting to cram GHGs into a pollutant definition, the more logical reading is that GHGs were not meant to be classified as “pollutants” under the CAA.
EPA should focus on realistic climate scenarios in assessing potential impacts
(C-2) A significant flaw in the scientific justification for the 2009 endangerment finding, as well as subsequent EPA efforts to regulated GHGs, is a general reliance on climate modeling that relies on extreme emissions scenarios. There are a range of emissions scenarios used by climate scientists as the data inputs for their modeling that projects climate impacts into the future. The most extreme of these scenarios is known as Representative Concentration Pathway 8.5 (RCP 8.5) which posits an extreme future emissions scenario that is well beyond any track that global emissions currently follow. However, this extreme scenario and ones like it have the advantage of producing eye catching results like flooded cities and millions of deaths that help researchers get published in journals and garner media attention. But these phantom extreme results are completely irrelevant to public policy and administrative process.
Unfortunately, often a majority of the papers that are used in any climate assessment, whether by the EPA, the IPCC, or other international organizations, use extreme scenarios like RCP 8.5 and SSP 8.5. Whatever the usefulness of these papers in academic literature, they are not appropriate or relevant for administrative action. EPA regulatory action should consider trajectories and projections which are likely, not extreme scenarios that are not occurring. IER strongly urges EPA to ensure that the universe of studies included in regulatory climate change analyses is confined to plausible emissions scenarios.
