The Navajo Nation is one of three dozen tribes to oppose construction of the Dakota Access Pipeline. Arizona Public Radio’s Ryan Heinsius reports, the tribes have filed a brief against the U.S. Army Corps of Engineers regarding the project’s completion.

Navajo Nation President Russell Begaye says the decision to grant the easement for the pipeline violates the federal government’s trust responsibility with tribes. He says preserving the environment and sacred sites is part of long-standing tribal treaty obligations.

The brief filed in U.S. District Court claims the Dakota Access Pipeline puts the Standing Rock Sioux’s water and natural and cultural resources in danger. It also calls for a full environmental impact statement for the pipeline.

Earlier this month, the Army of Corps of Engineers allowed the nearly 1,200-mile project to continue. It had been put on hold by the Obama administration to explore whether an alternative route was possible.