The suit, filed by environmental groups and several states, challenged the Environmental Protection Agency's contention that it was not authorized to regulate greenhouse-gas emissions from vehicles. Meanwhile, states began enacting their own regulations in the absence of EPA action. Well over a dozen have passed some sort of restrictions on tailpipe emissions of carbon dioxide.
The strict California rules require automakers to reduce greenhouse gas emissions from cars and light trucks by 25 percent and from sport-utility vehicles by 18 percent starting in 2009.
Automobile manufacturers had separately challenged California's authority to regulate emissions under the Clean Air Act. If the Supreme Court had ruled the other way, experts said, states such as Pennsylvania and New Jersey could have been vulnerable to similar challenges.
With Monday's 5-4 decision, "we know that the state, which already planned on moving forward, has the full and absolute authority to do so," said Suzanne Leta Liou, who works on energy and climate issues for the advocacy group Environment New Jersey.
Technically, said Nathan Wilcox, energy and clean air advocate with the group PennEnvironment, states need a waiver from the EPA to participate in the California program instead of using federal guidelines. But with the court ruling, he said, "it would seem that would all be moot."
John Hanger, president of Citizens for Pennsylvania's Future, said ramifications of the ruling go beyond the auto manufacturers' challenges to cleaner-car programs.
"It has solidified state and federal authority to treat carbon dioxide as a pollutant," he said. "The legislature is free to act. The governor is free to act."
Pennsylvania, Hanger said, is "just at the beginning of taking concrete steps and enacting rules to reduce carbon dioxide."
Gov. Rendell has pledged to present a strategy to "make Pennsylvania a leader in addressing climate change" by May 1.
Gov. Corzine signed an executive order in February calling for New Jersey to cut its greenhouse-gas emissions by 20 percent by 2020 and 80 percent by 2050.
Hanger said the Supreme Court ruling also removed a threat to any emerging green economy. Three foreign companies are bringing solar- and wind-power operations to the Philadelphia region.
"The decision was certainly good for the environment," Hanger said, "but in many ways it was absolutely essential for the business transformation."
Contact staff writer Sandy Bauers at 215-854-5147 or sbauers@phillynews.com.
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