washington u.s. power sector shift toward burn less coal use natural gas renewable energy derail supreme court rule obama administration limit carbon emissions state regulators utilities say wednesday u.s. supreme court decide 5-4 tuesday block environmental protection agency carbon emissions crackdown coal plant legal challenge resolve state may slow work compliance epa clean power plan experts say confident rule survive legal challenge d.c. circuit court make decision summer way really postpone inevitable say vicki arroyo executive director georgetown climate center even 27 state sue block rule officials work compliance plan state say continue decarbonize energy supply utilities across country already begin major shift away coal-fired electricity toward clean burn cheap natural gas renewables like wind solar fully expect many state continue efforts reduce greenhouse gas emissions legal authorities say bill becker director national association clean air agencies state like california colorado new york criticize high court decision vow pursue plan shift clean energy regardless delay epa rule meanwhile state like montana north dakota join lawsuit epa welcome breathe room stay provide even opponents rule say keep diversify power supply colorado democratic governor john hickenlooper say state keep work compliance leave disadvantage court uphold part clean power plan colorado challenge epa plan even though governor support state republican attorney general disagree legality rule economic impact montana governor steve bullock democrat oppose epa rule say state would put hold work group devise compliance options add still need address climate change embrace montana energy future say commit ensure term coal-producing north dakota one high emission reduction target meet rule regulators utilities keep work ways low power plant emissions say state health department chief dave glatt say epa plan give state sufficient amount time reasonable solutions pledge look reasonable step forward state coal-fired electricity decline 2015 generators shut 15,000 megawatts coal-fired power plant year low gas price drive power cost become uneconomical overhaul old coal plant even meet exist federal clean air rule ohio regulators say wednesday sure state respond court decision state major utilities already shift away coal american electric power co inc aep.n continue generate power natural gas renewable energy since price drop significantly say spokeswoman melissa mchenry add five-year extension federal renewable energy tax credit give aep incentive bring renewable energy mix make sense stick current plan position respond court ultimate decision future clean power plan say another ohio utility firstenergy corp fe.n say already retire number old coal plant 2012. court decision little impact supreme court decision change path say spokeswoman jennifer young think right thing complicate issue decision give state appropriate amount time develop compliance plan high court emissions rule wo n't deter clean energy drive