## Facts

- The Dakota Access Pipeline (DAPL) transports crude oil from North Dakota to Illinois; a contested segment crosses beneath Lake Oahe, a Missouri River reservoir.
- The Standing Rock Sioux Tribe and other tribal and environmental plaintiffs alleged that an oil spill at Lake Oahe would threaten tribal water supplies, treaty-protected hunting and fishing, and cultural and religious resources.
- The U.S. Army Corps of Engineers issued a federal easement for the Lake Oahe crossing based on an Environmental Assessment (EA) and a mitigated Finding of No Significant Impact (FONSI), rather than preparing an Environmental Impact Statement (EIS).
- The district court found the Corps’ NEPA review deficient, ultimately concluded an EIS was required, vacated the easement, and ordered the pipeline shut down and emptied while an EIS was prepared.
- The Corps appealed the NEPA and vacatur rulings; Dakota Access appealed vacatur and the shutdown remedy.

## Issues

1. Whether the Corps acted arbitrarily and capriciously under NEPA by issuing the Lake Oahe easement without preparing an EIS.
2. Whether unresolved disputes about spill risk, spill consequences, treaty impacts, and environmental-justice impacts made the project’s effects “highly controversial,” triggering an EIS.
3. Whether vacatur of the easement was an appropriate remedy under the APA.
4. Whether the district court properly applied the standards for injunctive relief when ordering the pipeline to be shut down and emptied.

## Decision

- The D.C. Circuit affirmed that the Corps violated NEPA by issuing the easement without preparing an EIS.
- The court agreed that serious scientific disputes and criticisms supported treating the effects of the easement decision as “highly controversial.”
- The court affirmed vacatur of the Lake Oahe easement while the Corps prepares an EIS.
- The court reversed the remedy to the extent it required the pipeline to be shut down and emptied, holding that the district court did not properly apply the independent standards governing injunctive relief.

## Legal Principles

- NEPA requires an EIS for a major federal action significantly affecting the environment; an agency may not rely on an EA/FONSI when significant effects are likely, including when effects are “highly controversial” due to unresolved, substantive scientific disputes.
- In evaluating controversy and significance, credible, technical criticisms—particularly from directly affected sovereign tribal governments—must be meaningfully addressed; agencies cannot dismiss them without reasoned analysis.
- NEPA analysis may require consideration of low-probability, high-consequence harms when a prudent decisionmaker would account for both the risk and magnitude of potential impacts.
- Under the APA, vacatur turns on the seriousness of the agency’s errors and the disruptive consequences of setting aside the action; vacatur may be appropriate when NEPA’s “hard look” requirement was not satisfied.
- Vacatur does not automatically justify injunctive relief; an injunction requires a separate equitable showing (including irreparable harm, balance of equities, and public interest) supported by an adequate record.

## Conclusion

The D.C. Circuit held that the Corps’ NEPA review for the Lake Oahe DAPL crossing was unlawful without an EIS and upheld vacatur of the easement, but it rejected the pipeline shutdown order because the district court failed to conduct a distinct injunctive-relief analysis.


Standing Rock Sioux Tribe v. U.S. Army Corps of Eng’rs, 985 F.3d 1032 (D.C. Cir. 2021)