The expected legal battle over the Obama administration’s coming limits on carbon emissions from existing power plants could provide a rarity for environmental litigation: a case for which there is scant court precedent. The Environmental Protection Agency is turning to a little-used provision of the Clean Air Act for its new rules, because carbon dioxide isn’t regulated under major programs that address air pollutants. The EPA says it has only used the section, called 111(d), to regulate five sources of pollutants since it was enacted in 1970—and none on the scale of CO2, a major greenhouse gas. Because the provision has been invoked so rarely, courts have had little opportunity to weigh in on it, creating the unusual circumstance in which potential challengers to the carbon rules would be litigating largely on a blank slate against the EPA. The Clean Air Act provision gives the agency authority to regulate […]