Joseph Goffman, an EPA official under President Barack Obama, said he feared that the Trump administration was trying to set a legal precedent that the Clean Air Act gives the federal government “next to no authority to do anything” about climate-changing emissions from the country’s power grid. The Obama rule, adopted in 2015, sought to reshape the country’s power system by encouraging utilities to rely less on dirtier-burning coal-fired power plants and more on electricity from natural gas, solar, wind and other lower or no-carbon sources.