## Facts

- The National Park Service (NPS) adopted a Backcountry Management Plan (BMP) for Canyonlands National Park to address increased visitation while protecting park resources.
- The BMP addressed motorized access on Salt Creek Road, including a disputed roughly ten-mile segment leading up Salt Creek Canyon.
- NPS prepared an Environmental Impact Statement evaluating alternatives and ultimately left most of Salt Creek Road, including the ten-mile segment, open to motorized use while closing a smaller portion.
- Southern Utah Wilderness Alliance (SUWA) challenged the BMP, alleging that continued motorized use would permanently impair unique park resources, contrary to the National Park Service Organic Act and the Canyonlands National Park Enabling Act, and also asserted APA and NEPA violations.
- The district court granted summary judgment for SUWA on the ten-mile segment and enjoined NPS from permitting motorized travel there, concluding the statutes unambiguously barred uses causing permanent impairment.
- Motorized-access groups intervened and appealed the injunction and statutory ruling.

## Issues

1. Whether the Organic Act and the Canyonlands Enabling Act unambiguously prohibit NPS from allowing motorized vehicle use on the ten-mile segment of Salt Creek Road.
2. If the statutes are ambiguous, whether the BMP reflects a permissible agency interpretation under Chevron step two and what deference is owed to NPS interpretations and policies.
3. Whether the district court erred by resolving the case at Chevron step one without evaluating evidence of impairment and the legal status of NPS policy statements.

## Decision

- The Tenth Circuit reversed the district court’s ruling that the BMP violated the Organic Act and Canyonlands Enabling Act based on an unambiguous statutory directive.
- The court held the Organic Act’s “unimpaired” mandate is ambiguous and requires interpretive judgment, requiring consideration of Chevron step two.
- The court determined NPS’s informal interpretations and internal guidance did not automatically qualify for Chevron deference.
- The case was remanded for the district court to conduct Chevron step-two analysis and assess, on the evidentiary record and any properly adopted NPS standards, whether allowing motorized use on the ten-mile segment is a permissible, non-impairing implementation of NPS’s statutory duties.

## Legal Principles

- Under Chevron, a court first asks whether Congress directly addressed the precise issue; if statutory text is ambiguous, the court proceeds to whether the agency’s interpretation is reasonable.
- The Organic Act’s direction to conserve park resources “unimpaired for the enjoyment of future generations” is not self-defining and may require agency interpretation when applied to specific uses.
- Agency interpretations set out in informal materials (such as policy statements, manuals, or enforcement guidance) generally do not receive Chevron deference; the formality and legal effect of the agency action matter.
- When statutory limits turn on “impairment,” courts may need a fact-based assessment of actual effects on park resources, not only a categorical statutory reading.

## Conclusion

The Tenth Circuit held that the governing park-protection statutes did not unambiguously bar motorized travel on the disputed road segment, reversed the injunction premised on that reading, and remanded for a Chevron step-two reasonableness inquiry tied to the record evidence of impairment and the legal status of any NPS impairment standards.


S. Utah Wilderness All. v. Dabney, 222 F.3d 819 (10th Cir. 2000)