## Facts

- Gray wolves in the northern Rocky Mountains were listed as endangered in 1974 after near-elimination from Montana, Idaho, and Wyoming.
- The U.S. Fish and Wildlife Service (FWS) implemented recovery planning and reintroduction efforts; wolf numbers later exceeded recovery targets in core recovery areas.
- FWS designated a “northern Rocky Mountain gray wolf” distinct population segment (DPS) and attempted delisting through rulemaking.
- A 2008 delisting rule for the DPS was challenged and vacated.
- In 2009, FWS issued a new final rule delisting the DPS in Montana and Idaho but retaining ESA protections in Wyoming due to Wyoming’s allegedly inadequate regulatory mechanisms.
- Environmental organizations sued under the Endangered Species Act (ESA) and Administrative Procedure Act (APA), and the case was presented on cross-motions for summary judgment.

## Issues

1. Whether the ESA permits FWS to delist only part of an already-designated DPS by removing ESA protections in some states while keeping the same DPS listed in another state.
2. Whether the 2009 rule was unlawful under the APA because it rested on a statutory interpretation that allows state-by-state “partial delisting” within a DPS.

## Decision

- The court granted plaintiffs’ motion for summary judgment in relevant part.
- The court held that the ESA does not authorize FWS to apply listed/delisted status to only part of a DPS’s range after the DPS has been designated.
- The court vacated the 2009 final rule that delisted wolves in Montana and Idaho but not Wyoming.
- ESA protections were reinstated for the entire northern Rocky Mountain gray wolf DPS, including Montana and Idaho.

## Legal Principles

- Under the ESA, a designated DPS is treated as the relevant “species-level” unit for listing and delisting decisions.
- The ESA’s text and structure do not provide authority for post-designation subdivision of a DPS to impose different legal statuses within the same DPS.
- Listing and delisting determinations must operate on the defined unit (the DPS) rather than on state-by-state fragments within that unit.
- An agency rule based on a statutory construction that exceeds ESA authority is unlawful under the APA and may be set aside as not in accordance with law.

## Conclusion

The court invalidated a delisting rule that split legal protections within a single wolf DPS, holding that FWS must list or delist a DPS as a whole; it vacated the rule and restored ESA protection across the DPS’s entire range.


Defenders of Wildlife v. Salazar, 729 F. Supp. 2d 1207 (D. Mont. 2010)