Overview:
The Standing Rock Sioux Tribe filed a federal lawsuit Friday challenging the Army Corps of Engineers’ approval of a new Dakota Access Pipeline easement beneath Lake Oahe, arguing that federal officials failed to adequately protect the Tribe’s drinking water, Treaty rights and sovereignty from the risk of an oil spill.
The Standing Rock Sioux Tribe filed a new federal lawsuit Friday against the U.S. Army Corps of Engineers and the Pipeline and Hazardous Materials Safety Administration (PHMSA), challenging federal decisions allowing the Dakota Access Pipeline (DAPL) to continue operating beneath Lake Oahe, the Tribe’s sole source of drinking water.
The lawsuit challenges the federal government’s environmental review and its May 21, 2026, Record of Decision authorizing a new easement for the pipeline’s crossing beneath Lake Oahe. The Tribe argues that federal officials failed to adequately address longstanding concerns about pipeline safety, potential oil spills, cultural resources, Treaty rights and the federal government’s obligations to the Tribe.
The legal action follows nearly a decade of opposition by the Tribe to the pipeline’s route beneath Lake Oahe, which lies less than one-half mile upstream from the Standing Rock Reservation.
“For ten years, Standing Rock’s concerns about this pipeline have not changed, and for ten years we have fought to protect our water, our Treaty rights, and our people. The Army Corps has now chosen to move forward without addressing those concerns. Until this pipeline is shut down, we will continue to defend what generations before us protected for our children,” said Standing Rock Sioux Tribe Chairman Steve Sitting Bear.
The Army Corps issued its Final Environmental Impact Statement on Dec. 19, 2025, following six years of environmental review. On May 21, 2026, the agency issued its Record of Decision adopting the analysis and authorizing a new easement with conditions addressing monitoring, leak detection, water supply contingency planning and other measures.
The Tribe maintains that the environmental review failed to adequately address its concerns and that the conditions do not sufficiently protect its water supply from the potential consequences of a catastrophic oil spill.
Pipeline capacity raises concerns
The Tribe also points to changes in the pipeline’s potential capacity since it was first proposed. Originally designed to transport approximately 574,000 barrels of oil per day, DAPL now has the potential to carry as much as 1.1 million barrels daily, nearly twice its original design capacity. The pipeline may also transport Canadian crude oil in addition to oil from the Bakken region.
“Lake Oahe is our sole source of drinking water. When you’ve increased that capacity to 1.1 million barrels of oil a day beneath that water, there is no room for an inadequate emergency response plan,” Sitting Bear said.
“We been waiting for years for the information to understand how a worst-case spill would actually be contained and cleaned up. We should not have to live with unanswered questions about the safety of our water.”
The Tribe said it has repeatedly sought adequate information about how a worst-case oil discharge affecting Lake Oahe would be contained and cleaned up. According to the Tribe, the federal government has not provided an adequate emergency response plan demonstrating how the community and its water supply would be protected in the event of a catastrophic spill.
An oil spill could threaten the health and welfare of the Standing Rock community, the Tribe said.
Lawsuit follows years of legal challenges
Standing Rock’s legal fight over DAPL dates to before construction began, when the Tribe raised concerns about the pipeline’s route beneath Lake Oahe and its proximity to the reservation.
In 2020, a federal court ruled that the Army Corps’ earlier environmental review was inadequate under the National Environmental Policy Act and vacated the Lake Oahe easement. The decision required the Corps to conduct a full Environmental Impact Statement, a process that culminated in the December 2025 report.
During that review, the Tribe raised concerns about pipeline safety, the operator’s spill and enforcement history, emergency response planning, environmental impacts, threats to its water supply, cultural resources and the federal government’s Treaty and trust responsibilities.
The Tribe contends that the final environmental analysis did not adequately resolve those issues.
The new lawsuit continues the legal struggle that developed alongside the #NoDAPL movement a decade ago. The Tribe argues that completing an environmental review and issuing a new easement do not relieve the federal government of its obligations under federal law or its Treaty and trust responsibilities.
Standing Rock has maintained that protecting Lake Oahe is essential to the health, safety and future of its people and that the federal government must address the risks posed by the pipeline’s continued operation.
