Last week, the Standing Rock Sioux celebrated what they believe is a ground-breaking legal victory in the protracted fight against the Dakota Access Pipeline.

A federal judge in Washington, D.C., ruled that the U.S. Army Corps of Engineers violated the National Environmental Policy Act (NEPA) in its expedited review of the pipeline, which was ordered by President Trump shortly after taking office. According to Judge James Boasberg, the Army Corps “did not adequately consider the impacts of an oil spill on fishing rights, hunting rights, or environmental justice.”

On Wednesday, the parties in the DAPL case will appear in court for a hearing about how to respond to the NEPA ruling. Oil could stop the flowing under Lake Oahe, the fourth-largest dam reservoir in the Dakotas. But that stoppage would be temporary.