Kennedy joined the court's four liberal justices in the 2007 ruling in Massachusetts v. EPA that said the agency has the authority under the Clean Air Act to limit emissions of greenhouse gases from vehicles.
Two years later, with Obama in office, the EPA concluded that the release of carbon dioxide and other heat-trapping gases endangered human health and welfare. The administration used that finding to extend its regulatory reach beyond automobiles and develop national standards for large stationary sources. Of those, electric power plants are the largest source of emissions.
The utility industry, the U.S. Chamber of Commerce and 13 states led by Texas are asking the court to rule that the EPA overstepped its authority by trying to regulate greenhouse gas emissions through the permitting program.
"Greenhouse gases are not included within the (permitting) program at all," Keisler said.
In addition to environmental groups, New York, California, Illinois and a dozen other states are supporting the administration, along with the American Thoracic Society, which filed a brief detailing the health costs of climate change.
Chief Justice John Roberts wondered if high school football games could fall under the EPA's regulation and Justice Stephen Breyer asked if the same would be true at a family gathering of his 500 relatives.
Verrilli's answer: "Human beings are actually net neutral on carbon emissions, and you will need a chemist to explain that to you. But it doesn't matter how many family members you have, you won't get to the limit," he said.
Follow Mark Sherman on Twitter: https://twitter.com/shermancourt
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