## Facts

- After EPA determined that greenhouse gases (GHGs) are “air pollutants” under the Clean Air Act (CAA), EPA issued four related actions regulating GHGs.
- EPA made an Endangerment Finding under CAA § 202(a) that six GHGs, in combination, may reasonably be anticipated to endanger public health or welfare.
- EPA issued a Tailpipe Rule setting GHG emission standards for new light-duty vehicles.
- EPA issued a Timing Rule interpreting when GHGs become “subject to regulation” for stationary-source permitting under the Prevention of Significant Deterioration (PSD) and Title V programs.
- EPA issued a Tailoring Rule that raised permitting thresholds for GHGs to limit PSD and Title V coverage initially to the largest stationary sources, citing administrative burdens from applying the CAA’s numeric thresholds to ubiquitous GHG emissions.
- Industry groups and several states petitioned for review, challenging the Endangerment Finding, Tailpipe Rule, and the Timing and Tailoring Rules, and disputing EPA’s interpretation that mobile-source regulation triggers PSD and Title V obligations for stationary sources.
- The petitions were consolidated in the U.S. Court of Appeals for the District of Columbia Circuit.

## Issues

1. Whether EPA’s Endangerment Finding under CAA § 202(a) was arbitrary and capricious or otherwise unlawful.
2. Whether EPA’s Tailpipe Rule for light-duty vehicles was arbitrary, capricious, or contrary to the CAA.
3. Whether regulating GHGs from motor vehicles makes GHGs “subject to regulation” such that PSD and Title V permitting requirements apply to stationary sources emitting GHGs.
4. Whether petitioners had Article III standing to challenge the Timing and Tailoring Rules, and, if so, whether those rules were lawful.

## Decision

- The court upheld EPA’s Endangerment Finding as consistent with the CAA and supported by the administrative record.
- The court upheld the Tailpipe Rule, holding that once EPA made a positive endangerment determination, EPA was required to issue motor-vehicle standards.
- The court held that, once GHGs are regulated under the CAA, PSD and Title V permitting requirements apply to stationary sources emitting GHGs under the statute’s “any air pollutant” language and related provisions.
- The court dismissed challenges to the Timing and Tailoring Rules for lack of standing because the rules reduced, rather than imposed, regulatory burdens on petitioners.

## Legal Principles

- CAA § 202(a) requires a scientific and technical judgment about endangerment; EPA need not consider policy consequences such as economic or programmatic effects at the endangerment stage.
- EPA may reasonably rely on existing scientific assessments and is not required to perform independent studies when addressing complex scientific questions.
- After a positive endangerment finding for motor-vehicle emissions, EPA lacks discretion to decline regulation under § 202(a) based on collateral effects elsewhere in the CAA.
- Once a pollutant becomes “subject to regulation” under the CAA, PSD and Title V permitting provisions applying to sources emitting “any air pollutant” are triggered according to their text.
- Article III standing requires a cognizable injury traceable to the challenged rule; regulated parties generally lack standing to challenge rules that alleviate the burdens they claim to suffer from the statutory scheme.

## Conclusion

The D.C. Circuit sustained EPA’s core greenhouse-gas program under the Clean Air Act by upholding the endangerment finding and vehicle standards and by holding that those regulations trigger stationary-source permitting obligations under PSD and Title V, while dismissing challenges to EPA’s burden-reducing Timing and Tailoring Rules for lack of Article III standing.


Coalition for Responsible Regulation, Inc. v. EPA, 684 F.3d 102 (D.C. Cir. 2012)