## Facts

- Congress amended the Clean Air Act (CAA) in 1990 to authorize EPA to treat eligible Indian tribes “in the same manner as a State” for specified CAA programs and to issue regulations defining covered provisions and tribal functions.
- EPA promulgated the Tribal Authority Rule (TAR) in 1998, allowing eligible tribes to implement air quality planning and permitting programs within reservations.
- EPA interpreted the 1990 CAA amendments as delegating federal authority to tribes to regulate air resources throughout reservation boundaries, including fee lands owned by nonmembers.
- The TAR defined “reservation” to include all land within reservation limits, including rights-of-way, trust lands, and fee lands, and also addressed certain Indian country/trust lands associated with tribes.
- Arizona Public Service Company and other industry and state petitioners sought judicial review, arguing EPA exceeded statutory authority and that tribal regulation of nonmembers conflicted with federal Indian law limits.
- Tribes intervened in support of EPA.

## Issues

1. Whether the 1990 CAA amendments authorize EPA to treat tribes as having regulatory authority over air quality on all lands within reservation boundaries, including nonmember-owned fee lands, based on a congressional delegation of federal authority.
2. Whether EPA lawfully defined “reservation” for CAA purposes to include trust lands and certain Indian country, including parcels associated with tribes that may lie outside formally established reservation boundaries.
3. Whether EPA’s interpretations were permissible under administrative law principles (including Chevron) and consistent with federalism and federal Indian law doctrines invoked by petitioners.

## Decision

- The court largely denied the petitions for review and upheld the TAR’s core framework.
- The court sustained EPA’s interpretation that the CAA amendments delegate federal regulatory authority to eligible tribes over air quality within reservation boundaries, including over nonmember fee lands.
- The court held that limits derived from cases addressing inherent tribal sovereignty over nonmembers did not control where Congress delegated authority within a federal regulatory program.
- The court generally approved EPA’s approach to defining “reservation” by reference to administrable Indian-law concepts, but granted the petitions in part and remanded a narrow portion concerning specific trust-land/boundary classifications where EPA’s explanation or record support was inadequate.
- One judge concurred in part and dissented in part, disagreeing with a portion of the majority’s analysis while not rejecting the overall validity of the TAR.

## Legal Principles

- When Congress authorizes EPA to treat tribes “in the same manner as a State” and directs EPA to specify applicable provisions and functions, EPA may recognize and implement tribal regulatory authority as a delegation of federal power within a cooperative federal scheme.
- Under Chevron, if the CAA does not clearly specify the geographic scope of tribal authority, EPA may fill the statutory gap with a reasonable interpretation, including an approach aimed at avoiding parcel-by-parcel “checkerboard” regulation within a reservation.
- Federal Indian law limits on inherent tribal authority over nonmembers do not foreclose Congress from delegating regulatory authority to tribes over persons and lands within reservation boundaries as part of a federal program.
- EPA may adopt a workable definition of “reservation” for CAA administration that draws on recognized categories of Indian country and related concepts, but it must adequately explain and support the inclusion of particular lands when boundaries or status are contested.

## Conclusion

The D.C. Circuit upheld EPA’s Tribal Authority Rule as a valid implementation of the Clean Air Act’s authorization to treat qualifying tribes like states and to delegate federal air-program authority across reservation boundaries, including nonmember fee lands, while remanding only a limited portion of the rule concerning insufficiently explained trust-land classifications.


Arizona Pub. Serv. Co. v. EPA, 211 F.3d 1280 (D.C. Cir. 2000)