The coalition said Thursday attorneys filed with the 9th Circuit appeals court, continuing their challenge of the 2015 approval of a lease extension for the Navajo Mine and the Four Corners Power Plant.
A judge tossed the case in September, citing tribal sovereignty. The judge argued the mine is owned by a corporation created by the Navajo Nation, making it immune to legal challenges.
Opponents of the lease argued the U.S. Interior Department and other agencies did not consider clean-energy alternatives or possible effects on endangered species.
The plant provides electricity to customers throughout the Southwest.