ALBUQUERQUE, N.M. (AP) — A U.S. judge is citing tribal sovereignty in dismissing a legal challenge filed by environmental groups over the federal government's decision to allow continued operations at a coal-fired power plant and adjacent mine near the Arizona-New Mexico border. The groups were targeting the 2015 approval of a lease extension for the Navajo Mine and the Four Corners Power Plant, which provides electricity to customers throughout the American Southwest. They argued the U.S. Interior Department and other agencies did not consider clean-energy alternatives or possible effects on endangered species. The judge tossed the case since the mine is owned by a corporation created by the Navajo Nation, meaning it has immunity from such legal challenges. The judge said the case could not move forward without the mine as a defendant.