Aides said the bill signed on Thursday would help the state's air quality. California also approved the nation's most stringent rules to reduce auto emissions linked to global warming this week.

But classic car hobbyists argued their cars have little effect on the state's smog.

"We're not too excited about it. The impact on the environment by classic cars is minimal," said John Halstead, president of the Bakersfield Camaro Club. "Most of the cars don't make it out of the garage for any other reason than for car shows once or twice a month in the summer."

The exact number of classic cars in California is unknown, but the state has hundreds of clubs for car hobbyists.

Leno, on whose show Schwarzenegger announced he would run for governor, protested personally against the bill, said Marva Diaz, legislative director for Assembly Member Sally Lieber, who wrote the bill.

Leno called Lieber's office twice to register his displeasure, Diaz said.

"He was very upset the first time," Diaz said. "He thought his whole collection would have to be smog-checked."

"The second time he called he was upset because he had been told the assemblywomen had said on the radio that he supported the bill," Diaz said. "He wanted to make sure it was clear to me to tell her that he remained opposed."