New rules from the Environmental Protection Agency governing air quality are threatening to shut down two coal-fired power plants in Northeast Texas. The owner of the plant, Luminant, has filed suit against the EPA to delay enforcement of the so-called Cross-State Air Pollution Rule and said the two closures would force 500 layoffs and could lead to rolling blackouts. Company and state officials protested that Luminant needed more time to meet the new regulation and said Texas was not told of the rule until six months before it was to take effect.