In summary
Trump rescinded the legal foundation for U.S. climate policy. California is preparing to sue — and may try to write its own rules.
The Trump administration formally rescinded the legal foundation of federal climate policy Thursday — setting up a new front in California’s long-running battle with Washington over emissions rules.
“Today, the Trump EPA has finalized the single largest act of deregulation in the history of the United States of America,” EPA Administrator Lee Zeldin said at a White House press conference. “Referred to by some as the holy grail of federal regulatory overreach, the 2009 Obama EPA endangerment finding is now eliminated.”
After the U.S. Supreme Court ruled the federal government may regulate greenhouse gases if they were found to endanger public health, the U.S. Environmental Protection Agency issued a scientific determination that greenhouse gases indeed were a threat. By withdrawing its own so-called “endangerment finding,” the EPA is abandoning its justification for federal tailpipe standards, power plant rules and fuel economy regulations.
California opposed the withdrawal of the endangerment finding when it was proposed last year, and is expected to sue over the decision.
California Air Resources Board executive director Steven Cliff testified at the time that the move ignored settled science.
“Thousands of scientists from around the world are not wrong,” Cliff said in his testimony. “In this proposal, EPA is denying reality and telling every victim of climate-driven fires and floods not to believe what’s right before their eyes.”
Gov. Gavin Newsom said in a statement Thursday that California would take the Trump administration to court over the decision.
“Donald Trump may put corporate greed ahead of communities and families, but California will not stand by,” Newsom said. “We will continue to lead because the lives and livelihoods of our people depend on it.”
Other states and environmental groups have also indicated they could sue. They include Massachusetts, which was part of the coalition of states that sued to force the federal government to curb greenhouse gases nearly two decades ago.
Eliminating the federal basis for regulating planet-warming gases will not halt California’s climate policies, most of which – from California’s market-based approach to cutting carbon pollution to clean energy mandates for utilities — rest on state law.
In fact, the decision may open the door for California to set its own greenhouse gas standards for vehicles, a possibility that lawmakers and regulators are actively weighing.
The reversal in federal policy could also undercut arguments that federal law blocks state lawsuits against oil companies and boosts interest in expanding California’s authority over planet-warming pollution within its borders.
California prepares for a fight
Ann Carlson, a UCLA law professor and former federal transportation official, has argued that aggressive federal action against climate policy “could, ironically, provide states with authority they’ve never had before.”
Writing in the law journal Environmental Forum, Carlson theorized that California could attempt to regulate greenhouse gas emissions from cars and trucks directly under state law.
Federal law has preempted most states from setting local vehicle emission standards; California has, through a series of waivers granted under federal clean air law, obtained permission to set stricter standards than the federal government does.
This could help California’s efforts “in the long run,” Carlson wrote in an email Wednesday, “but of course withdrawing the United States from all efforts to tackle climate change is a terrible move. We should be leading the global effort, not retreating.”
In California, where cars and trucks account for more than a third of the state’s greenhouse gas emissions, California regulators at the air board and lawmakers are weighing in. When asked last year by CalMatters whether the air board would consider writing its own rules, Chair Lauren Sanchez said, “All options are currently on the table.”
“This is definitely a conversation,” Assemblymember Cottie Petrie-Norris, a Democrat from Irvine, said during a Wednesday press conference held by the California Environmental Voters. “So stay tuned.”
Ripple effects in court and Sacramento
If Washington formally exits the field of carbon regulation, states may argue they have broader room to pursue liability claims tied to wildfire costs and other climate impacts, experts said.
California has sued major oil companies as recently as 2023, in an attempt to hold them responsible for climate impacts. Oil companies have frequently cited federal oversight as a reason to dismiss climate-damage lawsuits against them.
“California is struggling with wildfire costs, for example, which are linked strongly to a warming climate,” said Ethan Elkind, a climate law expert at UC Berkeley. “I think that opens up a lot of legal avenues for states like California.”
The federal pullback has prompted lawmakers to consider expanding the Air Resources Board’s powers.
Assemblymember Robert Garcia, a Democrat from Rancho Cucamonga, this week introduced a bill aimed at affirming the state’s power to curb pollution from large facilities that generate heavy truck traffic, such as warehouses and ports, which concentrate diesel exhaust in nearby communities.
“It’s no secret that the federal government and California are not seeing eye to eye — we’re not on the same page,” Garcia said at Wednesday’s news conference. “This is an opportunity for our state, for California to step in.”
