Breaking with some of their biggest rivals, General Motors, Fiat Chrysler and Toyota said they were intervening on the side of the Trump administration on Monday in an escalating battle with California over fuel economy standards for automobiles.
Their decision pits them and others against their peers, including Honda and Ford, who this year reached a deal to follow California’s stricter rules. It represents the latest dramatic twist in one of the Trump administration’s most consequential rollbacks of regulations designed to fight climate change.
The Trump administration has proposed a major weakening of federal auto emissions standards set during the Obama administration, prompting California to declare that it will go its own course and keep enforcing the earlier, stricter standards. The automakers siding with the administration, led by the industry group Global Automakers, say that the federal government, not California, has the ultimate authority to set fuel economy standards for passenger cars and trucks.
The legal fight between the Trump administration and California over auto pollution rules has swelled into a sweeping battle over states’ rights and climate change that is likely to be resolved only once it reaches the Supreme Court. Its resolution could have repercussions affecting pollution regulations across the United States, as well as states’ rights to set their own environmental laws and the future contours of the auto industry.
Under the decades-old Clean Air Act, California has the power to write its own clean-air rules, and the state has taken the Trump administration to court to defend its authority.
Several other states have pledged to follow California’s lead in enforcing stricter standards for auto emissions, meaning that their actions have the potential to split the United States auto market, with each side selling vehicles with different sets of pollution standards.
In July, Honda, Ford, Volkswagen and BMW sided with California in the battle, striking a deal with the state to follow more stringent standards close to the original Obama-era rules. That surprise agreement, which prompted an angry response from President Trump, would allow those automakers to meet both federal and state requirements with a single national fleet, avoiding a patchwork of regulations.
The automakers that intervened on Monday in the legal battle are instead siding with the Trump administration, though John Bozzella, chief executive of the Association of Global Automakers, made clear the group still hoped for a middle ground. “We can still reach an agreement that is supported by all the parties,” Mr. Bozzella said.
Still, he said, the industry has “historically taken the position that fuel economy is the sole purview of the federal government — though it doesn’t have to come to that.” He added that the automakers’ decision to intervene in the lawsuit was aimed at supporting the idea that there should be one national standard, and not aimed at determining what the ultimate standard should be.
The Obama-era national fuel economy standard, requires automakers to build vehicles that achieve an average fuel economy of 54.5 miles per gallon by 2025, which would eliminate about 6 billions tons of carbon dioxide pollution over the lifetime of those vehicles.
Carbon dioxide is one of the most important greenhouse gases, and in the atmosphere contributes to the warming of the planet.
The Trump administration is planning to roll back that standard to about 37 miles per gallon.
California representatives were not immediately available for comment.
Nearly two dozen other states have filed suit against the Trump administration, alongside California, over the emissions rules. California and the other states maintain that its authority to set standards on tailpipe pollution was granted lawfully by Congress as part of the Clean Air Act, one of the country’s foundational environmental laws, and that its revocation would be unlawful.
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