Thus far, Oregon is the only other state with a carbon fuel standard like California’s. But Mr. Sperling said that as vehicle fuel efficiency rules also took effect and the policies combined to reduce oil use, he expected that other states would follow suit. “This is the best model in the world right now for how to reduce the carbon intensity of our fuels,” Mr. Sperling said. “It’s a model that I think we’re going to see more and more other places imitate.”

But any further efforts to push down petroleum consumption will run up against the same muscular opposition from the oil industry that was able to hand Mr. Brown one of his few big political defeats in recent years.

The change will hit consumers in the pocketbook: The state’s own projections estimate that fuel costs could rise 13 cents per gallon by 2020 as a result of the low-carbon standard.

The Western States Petroleum Association, which led the charge against the 50 percent reduction, argued that low-carbon fuel rules had not been a success so far. “While there have been some advances in the biofuels technology since the standard was introduced,” said the association’s president, Catherine Reheis-Boyd, in a written statement, “there are still not enough low-carbon biofuels available in sufficient quantities to allow refiners to comply with the regulations.”

But environmental groups pointed to advances in natural gas, biodiesel and the growing use of hybrid and electric cars in California as proof that the standard would not be difficult to meet. A spokesman for the Air Resources Board said on Friday that many oil producers were already hitting what the annual carbon reduction targets would have been, even though the targets were suspended during the legal proceedings. “We are on a path towards decarbonizing our transportation, and it’s not going to be stopped,” said Adrienne Alvord, the Western states director for the Union of Concerned Scientists.