This rule was published pursuant to the Clean Air Act which gives the EPA broad authority to set pollutant levels. These regulations were not promulgated on a whim. It's the actions of the president that seem to be on a whim.   Federal rules and executive branch actions are routinely challenged in court. Maybe you want to check how many times Pruitt has sued the EPA. You MAGAphant comment clearly reflects yours and Trumps lack of understanding of the three branches of govt.