The US supreme court has rejected a case by the Dakota Access oil pipeline operator to avoid a legally mandated environmental review, in a major victory for tribes and environmentalists campaigning to permanently shut down the polluting energy project. Energy Transfer, the pipeline operator, had sought to overturn a legal victory won by the Standing Rock Sioux Tribe in 2020 that struck down a key federal permit that violated the National Environmental Policy Act (Nepa). On Tuesday the US supreme court rejected the company’s bid to challenge the 2020 ruling, which required the US army corps of engineers to conduct a comprehensive environmental impact statement (EIS). As a result, the lower court’s decision remains intact and the army corps must complete a review of the pipeline’s route underneath Lake Oahe, which straddles the border of North Dakota and South Dakota, that complies with Nepa. Indigenous communities rely on the lake, which they consider sacred, for drinking water and food. The ruling is a huge victory for North Dakota tribes including the Standing Rock Sioux Tribe which rallied support from across the world and sued the US government in a campaign to stop the environmentally risky pipeline being built on tribal lands. It signals the end of the litigation road for the Texan energy company, but the pipeline, known as DAPL and open since 2017, will continue to operate as the review is carried out. “The litigation concerning the pipeline is over, but the fight continues,” said attorney Jan Hasselman from EarthJustice, the legal non-profit that represents the Standing Rock Sioux Tribe in the case. “We call on the administration to close the pipeline until a full safety and environmental review is complete. DAPL never should have been authorized in the first place, and this administration is failing to address the persistent illegality of this pipeline,” Hasselman added. The eventual future of the fossil fuel project was not part of the supreme court appeal, but Energy Transfer said in court papers that the pipeline was “vulnerable to a shutdown” with the new environmental review pending. The Standing Rock tribe, along with the Yankton Sioux, the Oglala Sioux and the Cheyenne River Sioux tribes, have long opposed the biggest pipeline out of the Bakken shale basin, which runs about 1,170 miles from North Dakota to Illinois. The disputed section under Lake Oahe, an artificial reservoir on the Missouri River, is 1.7 miles long. The tribes fear an oil spill which could be catastrophic. The legal battle dates back to 2016 when the Obama administration denied permits for the pipeline to cross the Missouri river and ordered a full EIS to analyze alternative routes and the impact on the tribe’s treaty rights. In his first week in office, Donald Trump signed an executive order to expedite construction. Construction of the 1,200-mile pipeline was completed in June 2017. The tribe challenged the permits – and won. As a result, the corps was ordered to redo its environmental analysis, which it did without taking into consideration tribal concerns or expert analysis. The pipeline continued to transport oil from North Dakota to Illinois. The tribes and EarthJustice, an environmental law not-for-profit group, sued again. In March 2020, federal judge James Boasberg, an Obama appointee, said the environmental analysis by both the companies behind the pipeline and the corps was severely lacking. In his ruling, Boasberg said that the company’s abysmal safety record of the pipeline parent company “does not inspire confidence”. The Biden administration urged the supreme court not to hear the subsequent appeal by Energy Transfer, saying the pipeline operator concerns about a shutdown were overstated. The company declined to comment.