## Facts

- The Clean Air Act requires the EPA to set national ambient air quality standards (NAAQS) for certain pollutants based on air quality criteria.
- In 1997, the EPA revised the NAAQS for ozone and particulate matter under Clean Air Act §109(d)(1).
- Industry groups and several States challenged the revised standards.
- Challengers argued that §109(b)(1) delegated legislative power without an intelligible principle, that EPA had to consider implementation costs when setting NAAQS, and that EPA misread statutory provisions governing implementation for ozone nonattainment areas.
- The D.C. Circuit held §109(b)(1) unconstitutional as construed, remanded for a limiting construction, reaffirmed that costs cannot be considered in setting NAAQS, and ruled on the meaning of ozone implementation provisions in Part D.

## Issues

1. Whether Clean Air Act §109(b)(1) unconstitutionally delegates legislative power to the EPA.
2. Whether the EPA may consider implementation costs when setting NAAQS under §109(b)(1).
3. Whether the court of appeals had jurisdiction to review EPA’s interpretation of ozone implementation provisions in Part D, and whether EPA’s interpretation was lawful.

## Decision

- The Supreme Court unanimously held that §109(b)(1) is not an unconstitutional delegation because it supplies an intelligible principle.
- The Court held that §109(b)(1) does not permit EPA to consider implementation costs when setting NAAQS.
- The Court held that the court of appeals had jurisdiction to review EPA’s interpretation of the ozone implementation provisions in Part D.
- The Court rejected EPA’s interpretation of those implementation provisions and remanded for proceedings consistent with the Court’s reading of the statute.
- Justice Thomas concurred, questioning whether the intelligible-principle test is sufficient in all cases.

## Legal Principles

- Congress may confer regulatory authority on an agency if it sets an intelligible principle guiding the agency’s exercise of discretion.
- A directive to set standards “requisite to protect the public health” with “an adequate margin of safety” is an intelligible principle and falls within established nondelegation precedent.
- Clean Air Act §109(b)(1) requires NAAQS to be set on health-based criteria; statutory silence on costs in §109(b), combined with express cost language elsewhere in the Act, bars importing a cost factor into NAAQS-setting.
- Cost considerations may be addressed at later stages of regulatory design and implementation, but not in the initial setting of NAAQS under §109(b).
- Courts may review EPA’s statutory interpretations tied to NAAQS promulgation, and EPA’s reading of Part D must be reasonable in light of the Act’s structure, including the relationship between general and pollutant-specific nonattainment provisions.

## Conclusion

The Court sustained EPA’s authority to set NAAQS under §109(b)(1) against a nondelegation challenge, held that NAAQS must be set without regard to implementation costs, and clarified that courts may review, and must enforce, the statutory constraints Part D places on implementing revised ozone standards.


Whitman v. American Trucking Ass'ns, Inc., 531 U.S. 457 (2001)