A federal judge ruled Wednesday night that the environmental review for the $3.8 billion Dakota Access oil pipeline must be redone to assess the risk of an oil spill under Lake Oahe in North Dakota.

Tribal groups, which have tried to block the pipeline from crossing the lake for nearly two years, took U.S. District Court Judge James Boasberg’s decision as a major victory in their fight. But the judge’s order won’t stop the pipeline from shipping oil 1,200 miles to Illinois.