May 26, 2020

May 26, 2020

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New Supreme Court Ruling On EPA Authority Over Greenhouse Gases (GHGs) – Little Clarification on the 111(d) Regulations

Last week, the United States Supreme Court issued a significant decision in Utility Air Regulatory Group v. EPA, that substantially restricts the authority of the U.S. Environmental Protection Agency (EPA) to regulate greenhouse gas emissions (GHGs) from stationary sources under the Clean Air Act’s Prevention of Significant Deterioration (PSD) and Title V permitting programs. The Supreme Court’s decision holds that EPA may not impose permitting requirements on facilities based solely on their emissions of GHGs, but may regulate GHG emissions under the PSD and Title V programs, only if a facility is otherwise subject to major source permitting requirements.


EPA interpreted the Clean Air Act to require stationary sources to obtain construction and operating permits under the PSD and Title V programs whenever a facility emits GHGs above certain threshold levels. The threshold levels EPA chose were different than the levels established by Congress in the Clean Air Act, because the statutory levels when applied to GHGs were too low (as compared to criteria pollutant thresholds), and applying those levels to GHG emissions would lead to “absurd results” by subjecting millions of small sources such as shopping malls, hospitals and churches to major source permitting requirements. These thresholds were established in what is known as the “Tailoring Rule.”

The Tailoring Rule triggered regulatory review for two different source categories (for purposes of GHG emissions): sources that were already subject to major source review under the Clean Air Act because of emissions of criteria pollutants in excess of the major source thresholds (so-called “anyway” sources) and those sources that would trigger major source review for the first time based solely on emissions of GHGs in excess of the “tailored” thresholds set by EPA.


The Supreme Court’s divided 5-4 decision, authored by Justice Scalia, held that EPA’s rulemakings setting “tailored” thresholds for GHGs were invalid. The Court, however, stopped short of holding that GHGs could not be regulated at all under the PSD and Title V programs.

Specifically, the Supreme Court upheld EPA’s approach of requiring “best available control technology” (BACT) standards for GHGs for those sources otherwise required to obtain a PSD permit (the “anyway” sources). The Court emphasized, though, that it was not approving EPA’s current approach to BACT regulation of GHGs, or of any future approach that EPA might adopt. The Supreme Court categorized this aspect of the holding as having only a small impact on the regulated community, stating that 85 percent of all GHG major sources are “anyway” sources, while only an additional 3 percent would be major sources under the GHG tailoring trigger.

The Supreme Court also reaffirmed its decision in Massachusetts v. EPA, which held that GHGs qualify as an “air pollutant” for purposes of the term’s general definition in the Clean Air Act.

Takeaways and Import of This Case on 111(d) Regulations:

1)      GHG Emissions Alone Do Not Trigger Major Source Permitting Obligations – The principal legal holding of the decision is also considered the most significant from a practical perspective. Stationary sources cannot, under the Court’s ruling, be subject to permitting requirements based solely on their emissions of GHGs. The Court’s math on the number of sources impacted by this core aspect of the decision is questionable, and there is suspicion that many potentially major sources were specifically planning facilities to avoid major source permitting review by designing facilities to avoid the tailoring trigger for GHGs. In short, the impact of this decision is potentially very significant for the regulated community.

2)      Greenhouse Gas Emissions Are an “Air Pollutant” Subject to Regulation under the Clean Air Act. While the decision holds that GHGs are not an “air pollutant” for purposes of triggering PSD and Title V permitting requirements, it stops short of holding that GHGs are not an “air pollutant” for other purposes. To the contrary, the Court affirmed its prior holding in Massachusetts v. EPA, that the term “air pollutant,” as generally defined in the Clean Air Act, includes GHGs.

3)      Mixed Signals About EPA’s Authority to Issue NSPS Regulations Under 111(d). The Supreme Court was careful to note that EPA’s authority to regulate GHG emissions under the New Source Performance Standards (NSPS)  were not at issue and did not need to be addressed (that is, the Court specifically did not address the proposed 111(d) rules).

a)      As noted above, the Supreme Court reinforced that GHGs may be regulated as an air pollutant under other aspects of the Clean Air Act (just not PSD or Title V). Though the Supreme Court found that EPA was right to determine that the statutory thresholds for major source review would lead to “absurd results” in the PSD and Title V context for major source triggers, the Court said nothing about EPA’s authority to regulate under the NSPS provisions of Section 111(d). One way to interpret the decision is that it cloaks EPA with apparent authority to address GHGs as an “air pollutant” under Section 111(d).

b)      On the other hand, the Supreme Court took a stern tone in admonishing EPA for over-stepping its bounds. As an example, the Court warns EPA: “[W]hen an agency claims to discover in a long-extant statute an unheralded power to regulate ‘a significant portion of the American economy,’ we typically greet its announcement with a measure of skepticism.” That statement was directed at EPA’s attempt to regulate GHGs in the PSD and Title V programs, but the same argument might be made in the 111(d) context.


There are still many questions to be answered surrounding the 111(d) regulations proposed by EPA. This decision clarifies the overall picture of GHG regulation slightly, but does little to provide a clear boundary on EPA’s authority over GHGs. No doubt, this decision will be cited by both those in favor and those against the 111(d) regulations.

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About this Author

Adam DeVoe, Environmental Litigation Attorney, Lewis Roca Law Firm
Of Counsel

Mr. DeVoe is in the firm’s Government and Regulatory Affairs practice group. His practice is focused ‎on environmental litigation and compliance, natural resources law, and water rights. He represents ‎private and public companies in virtually all facets of environmental compliance, environmental ‎planning, environmental due diligence, and risk management. Mr. DeVoe specializes in air quality ‎compliance, air quality regulatory defense, and air quality litigation matters. He also has broad ‎experience with environmental matters ranging from water quality to endangered species,...