The Army Corps of Engineers approved a key easement Wednesday night to allow the completion of the 1,100-mile Dakota Access oil pipeline, as native groups protested outside the White House to kick off the next phase of mass resistance against the project.

The Standing Rock Sioux Tribe led an intense protest campaign last year to prevent the company building the pipeline, Energy Transfer Partners, from building a short segment of the project under Lake Oahe. The tribe argued that the oil pipeline would jeopardize their only source of freshwater.