## Facts

- The U.S. Army Corps of Engineers granted Dakota Access, LLC an easement allowing the Dakota Access Pipeline (DAPL) to cross under Lake Oahe, a federally managed portion of the Missouri River near the Standing Rock and Cheyenne River Sioux Reservations.
- Tribal plaintiffs challenged the Corps’ NEPA compliance, focusing on oil-spill risk and potential harm to water supplies, treaty-protected resources, and environmental justice interests.
- After earlier proceedings, the Corps conducted additional analysis on remand but reaffirmed a Finding of No Significant Impact (FONSI) and declined to prepare an Environmental Impact Statement (EIS).
- The Tribes moved for summary judgment and sought vacatur of the Lake Oahe easement and a court-ordered shutdown of pipeline operations pending NEPA compliance.

## Issues

1. Whether NEPA required the Corps to prepare an EIS for the Lake Oahe easement because the action’s environmental effects were “highly controversial” due to unresolved expert disputes, particularly over oil-spill risk and consequences.
2. If the Corps violated NEPA, whether the proper remedy included vacatur of the easement and an injunction requiring DAPL to cease operations and be emptied pending completion of an EIS.

## Decision

- The court held the Corps violated NEPA by failing to prepare an EIS for the Lake Oahe crossing.
- The court found the easement’s effects were “highly controversial” in the NEPA sense because of substantial, unresolved scientific disputes over spill risk, leak detection, response capabilities, and worst-case impacts.
- The court ruled the Corps’ mitigated FONSI and EA-level review did not satisfy NEPA’s “hard look” obligation in light of these disputes and was arbitrary and capricious under the APA.
- Applying Allied-Signal factors, the court vacated the Lake Oahe easement, concluding the seriousness of the NEPA error outweighed the disruptive consequences of vacatur despite the pipeline’s operation.
- The court ordered DAPL to shut down and be emptied of oil while the Corps prepared the required EIS.

## Legal Principles

- NEPA requires an EIS for major federal actions significantly affecting the environment; an EA and FONSI are insufficient where significance factors indicate likely significant effects.
- “Highly controversial” effects under NEPA concern substantial expert or agency dispute about the size, nature, or effect of the action, not public or political controversy.
- NEPA’s “hard look” requires an agency to meaningfully address material criticisms and scientific disagreements in the administrative record.
- Under the APA, a failure to prepare an EIS when required, or to adequately explain why an EIS is unnecessary, is arbitrary and capricious.
- Under Allied-Signal, courts weigh (1) the seriousness of the agency’s deficiencies and (2) the disruptive consequences of vacatur to decide between remand without vacatur and vacatur.
- Equitable relief beyond vacatur (such as a mandatory shutdown) requires justification under traditional equitable principles in addition to the NEPA/APA merits determination.

## Conclusion

The court concluded that unresolved, technical disputes over spill risk and impacts made the Lake Oahe easement decision “highly controversial” under NEPA, requiring an EIS; it therefore vacated the easement and ordered interim cessation of operations pending completion of the EIS.


Standing Rock Sioux Tribe v. U.S. Army Corps of Eng’rs, 471 F. Supp. 3d 71 (D.D.C. 2020)