## Facts

- EPA regulated greenhouse gas (GHG) emissions from new motor vehicles under the Clean Air Act (CAA), concluding that GHGs thereby became “subject to regulation” under the Act.
- EPA interpreted the CAA’s stationary-source permitting programs—Prevention of Significant Deterioration (PSD) and Title V—to require permits for stationary sources based on GHG emissions alone.
- PSD applies to construction or modification of a “major emitting facility,” generally defined by potential emissions of 250 tons per year (tpy) (or 100 tpy for certain categories) of “any air pollutant,” and requires “best available control technology” (BACT) for “each pollutant subject to regulation.”
- Title V requires operating permits for “major sources,” generally defined as sources with potential emissions of 100 tpy of “any air pollutant.”
- EPA concluded that applying the statutory 100/250 tpy thresholds to GHGs would sweep in many small sources and overwhelm permitting programs.
- To address that concern, EPA issued a “Tailoring Rule” that raised the emissions thresholds for GHG-based PSD/Title V applicability (e.g., 100,000 tons per year CO₂-equivalent) and phased in requirements.
- Industry groups and several states challenged EPA’s stationary-source GHG permitting approach; the D.C. Circuit largely upheld EPA’s actions, and the Supreme Court granted review on the stationary-source permitting questions.

## Issues

1. Whether the CAA compels or permits EPA to require PSD and Title V permits solely because a stationary source emits GHGs above the statutory 100/250 tpy thresholds.
2. Whether EPA may require sources already subject to PSD due to non-GHG pollutants to apply BACT to their GHG emissions.

## Decision

- The Court affirmed in part and reversed in part the D.C. Circuit.
- EPA lacked statutory authority to require PSD or Title V permits on the sole basis of a source’s potential GHG emissions.
- EPA lacked authority to “tailor” the statute by rewriting the unambiguous numerical thresholds Congress enacted for PSD and Title V.
- EPA could require PSD sources that are already subject to PSD permitting based on conventional pollutants (“anyway” sources) to apply BACT to GHG emissions.

## Legal Principles

- The Act-wide definition of “air pollutant” does not automatically control every use of that term across distinct CAA programs; statutory context can limit how a term operates in a specific provision.
- An agency may not revise clear statutory thresholds to avoid administrative burdens or to achieve policy objectives; numerical limits set by Congress must be applied as written.
- Claims of authority that would create a major, transformative expansion of regulatory coverage require clear congressional authorization.
- Under PSD, once a source is properly subject to PSD permitting, EPA may require BACT for each pollutant “subject to regulation” under the Act, including GHGs.

## Conclusion

The Court held that EPA could not expand PSD and Title V permitting to cover sources based solely on GHG emissions or alter Congress’s permitting thresholds by regulation, but it allowed EPA to require GHG BACT for sources already required to obtain PSD permits because of their conventional pollutant emissions.


Util. Air Regul. Grp. v. EPA, 573 U.S. 302 (2014)