“In its repeal, the Trump EPA is rehashing legal arguments that the Supreme Court already considered and rejected in Massachusetts v. EPA,” said Earthjustice, representing six of the litigants, in a statement. The court's conclusion that the agency has legal authority to regulate greenhouse emissions as a pollutant set the stage for EPA to issue its 2009 “endangerment finding.” Using a science-backed determination, EPA listed six greenhouse gasses, including carbon dioxide and methane, as harmful to public health and subject to emissions regulation under Section 202 (a) of the Clean Air Act.

In a statement, EPA Administrator Lee Zeldin said the rule exceeded the powers Congress granted the agency to regulate vehicle and engine emissions, based on a “robust analysis of the law following the [high court] decision in Loper Bright Enterprises v. Raimondo and West Virginia v. EPA.” 

EPA's decision is at “complete odds with the public interest and the best available science,” said Gretchen Goldman, president and CEO at the Union of Concerned Scientists, one of the plaintiffs. “Heat-trapping emissions and global average temperatures are rising—primarily due to the burning of fossil fuels—contributing to a mounting human and economic toll across the nation.”

But EPA also pointed to costs when announcing the rescission and removal of emissions standards, claiming the moves will save $1.3 trillion, including $2,400 per vehicle, “by removing the regulatory requirements to measure, report, certify and comply with federal GHG emission standards for motor vehicles, and repeals associated compliance programs, credit provisions and reporting obligations.” The agency did not explain how it had calculated those savings.

Plaintiffs: New Costs Would Offset Savings

Environmental and clean energy groups argue that any such savings would be offset by other resulting costs. 

“Rolling back tailpipe standards has real economic consequences, from higher fuel costs for consumers to significant job loss across the transportation and manufacturing sectors,” said Michael Berube, CEO of clean tech transportation group CALSTART, in a statement. He pointed to an October 2025 report from climate policy think tank Energy Innovation that estimated a $310-billion cost to consumers, based on associated higher gas costs, and a loss of 110,000 industry jobs. “Private-sector innovators and manufacturers have invested hundreds of billions of dollars into developing cutting-edge, cleaner, more-efficient vehicle technologies.”

While the endangerment finding's “most direct impact has been on vehicle emissions,” says Doug Hastings, partner at law firm Morgan Lewis with a focus on environmental law, “it is also a key scientific finding that has underpinned EPA’s assumptions regarding the impacts of climate in other regulations.” He points out that “EPA did not finalize its alternative conclusions on climate science in its current final rule.” In July 2025, the U.S. Energy Dept. issued a report from its Climate Working Group, perceived as an attempt to use science to undermine the conclusions of the endangerment finding determination. The findings were refuted by dozens of climate experts. 

Depending on if, and how, the Supreme Court ultimately rules, its decision could impact emissions regulation in other sectors, including buildings and industrial facilities.

While EPA is eliminating federal restrictions on tailpipe emissions, regulations still exist on the state level, including California and states like Oregon, Washington and New York that conform to California's tailpipe emissions standard. “California also has other more stringent regulations related to GHGs,” Hastings told ENR, including its Greenhouse Gas Reporting and Climate Related Financial Risk Disclosure Program. 

Still, other states are expected to follow EPA's path—most recently, Alabama, whose legislature on Feb. 17 approved a bill that would prohibit state regulation of pollutants and hazardous substances beyond levels set by the federal government,

EPA's decision, meanwhile, is creating uncertainty in its wake—from court challenges to construction investment decisions that may need to weigh removal of federal restrictions against local, state and international requirements and trends. It also may leave construction to contend with a constellation of discordant policies across the country. 

"The oil and gas industry has already publicly and privately lobbied EPA not to revoke its existing methane rules,” said Jeff Holmstead, partner at law firm Bracewell and former head of EPA's Office of Air and Radiation in the George W. Bush administration. “To be sure, the industry has asked EPA to revise a few requirements to make them more reasonable, but it prefers federal rules to state-by-state requirements, which many states would impose if EPA’s methane regulations were revoked.” 

Further down the line, he added, “this might actually force Congress to get involved in reaching a bipartisan agreement on actual climate change legislation—probably not during the Trump administration, but the business community would like to have the long-term certainty that would come with bipartisan legislation.”