The U.S. Supreme Court agreed last week to reconsider a lower court decision that would allow states to limit greenhouse gas emissions under federal common law as a “nuisance.” The case, American Electric Power v. Connecticut, could have major legal and environmental significance. It would give states and others the authority to sue power plants, chemical companies, and other industries to reduce their greenhouse gas emissions in the absence of federal regulations on those emissions. The lower court made its decision last year in a suit brought by Connecticut and seven other states, New York City, and several environmental groups and targeted at several electric utilities. The utilities argued that federal law prevents states from taking such legal action, but the states said that because the federal government has failed to regulate greenhouse gases, they are free to turn to protections afforded through federal common law. An earlier Supreme Court decision gave EPA authority to regulate greenhouse gases through the Clean Air Act, but EPA has yet to issue regulations, and the agency’s authority is being challenged by industry advocates in Congress.