The fight over cars and carbon dioxide moves today from the Supreme Court to a federal courtroom in Burlington, Vt., in a case that automakers say could reshape vehicles sold on the East and West Coasts.
The industry is suing to block a 2004 California regulation on global warming from taking effect. The rule would require a 30 percent cut in emissions of greenhouse gases from cars and trucks sold in Vermont and New York, which follow California’s air quality rules, to be fully phased in by the 2016 model year.
In court filings, automakers have argued that regulating the emissions will increase pollution, cause more traffic deaths and lead domestic automakers to stop selling most of their passenger models in states that adopt such regulations.
The companies have disputed that global warming is a problem, even though they have acknowledged it in different forums as a serious problem. And they tried, mostly unsuccessfully, to close much of this case to the public.
“This is a huge issue to consumers, because it may well determine what vehicles are available for them to purchase,” said Gloria Bergquist, a spokeswoman for the Alliance of Automobile Manufacturers, which includes General Motors, Toyota and most other large automakers. “If it’s a big issue for consumers, it’s a big issue to us.”
Environmental groups and the offices of the attorneys general in Vermont and New York, which is a party to the case, say the automakers are overstating the complexity and hardship of such a regulation.
“It’s that sky-is-falling approach, but the sky didn’t fall with catalytic converters,” Attorney General William H. Sorrell of Vermont said, referring to the antipollution technology forced on the industry in the 1970s.
Last week, in a 5-to-4 decision in Massachusetts v. Environmental Protection Agency, the Supreme Court ruled that the agency has the authority to regulate heat-trapping gases in automobiles. The Bush administration has long opposed that.
Instead, more than 12 states, including California, Massachusetts, New York and Vermont, have already or are in the process of moving to regulate such emissions.
California has the authority to set air-quality rules, and Northeastern states have long chosen to follow those rules instead of Washington’s. The Supreme Court victory was important for the states, because the approval of the environmental agency is needed before California can regulate emissions involving global warming.
Automakers have sued to block the California regulation in federal courts in California, Rhode Island and Vermont, though just the Vermont case has gone forward. That case is scheduled to enter the trial phase today.
The battle has exposed fault lines among automakers. Two trade groups representing the major manufacturers are involved in the suit, one dominated by domestic producers and one by foreign.
They have clashed in their legal strategies, and just G.M. and DaimlerChrysler, two of the more outspoken companies opposing the new regulation, are directly listed as plaintiffs. The trade groups had initially sued separately but are now plaintiffs in a consolidated suit.
The main legal argument uniting the industry is their contention that states cannot regulate carbon dioxide emissions because that would be little different from regulating fuel economy, and Washington has the sole authority to set mileage standards. The recent Supreme Court ruling, however, appeared to undermine that argument.
The industry estimates that the new regulation would impose a 50 percent increase in fuel economy for passenger cars and small sport-utility vehicles but a more modest increase for large trucks, effectively making it harder for a company like G.M. to bring smaller vehicles like the Chevrolet Malibu into compliance than its Hummers.
An expert hired by automakers said, according to court filings, that DaimlerChrysler, Ford Motor and G.M. “will need largely to exit” from the passenger car and small truck markets.
Environmental groups say the industry is ignoring the potential effects of its move to bolster alternative fuels like ethanol, as well as the advent of hybrid electric technology and other technologies.
Automakers argued in a court filing in January that “defendants make unsubstantiated predictions that global climate change is having a number of alarming adverse effects.”
Michael J. Stanton, the president of the Association of International Automobile Manufacturers, a plaintiff group, said in an interview the position did not represent the views of the mostly Asian automakers who are his constituents, some of whom are trying to create “eco-friendly” reputations.
“We believe that there is enough information out there to address climate change and we know that cars — passenger cars and light trucks — contribute, and we want to be part of the solution,” Mr. Stanton said.
The regulation California adopted in 2004 was to begin taking effect with 2009 models and to be phased in over eight years. President Bush and Congress more recently discussed fuel economy rules that could potentially accomplish similar reductions for gases tied to global warming, though no firm plan is in place.
Among other points, the industry says more fuel efficient cars could be dangerous, because they will be cheaper to drive and lead people to drive more and potentially have more accidents.
“Everybody’s getting a good laugh out of the safety claim,” said David Bookbinder, a lawyer for the Sierra Club, which is a party to the case. “Detroit is saying it’s a bad idea for everybody to drive more.”