Legal experts are examining the complex procedural and legal hurdles that would face any attempt to rescind the Environmental Protection Agency’s 2009 Greenhouse Gas Endangerment Finding, which serves as the legal foundation for most federal climate regulations.
The 2009 finding determined that greenhouse gases endanger public health and welfare, providing the legal basis for EPA to regulate carbon dioxide and other greenhouse gas emissions under the Clean Air Act. Since its adoption, the finding has underpinned vehicle emission standards, power plant regulations, and other federal climate policies.
“The endangerment finding is really the cornerstone of federal climate policy,” said Michael Gerrard, director of the Sabin Center for Climate Change Law at Columbia University. “Without it, EPA’s authority to regulate greenhouse gases becomes much more limited.”
Any effort to rescind the finding would face significant legal and procedural obstacles, according to environmental law experts. The Administrative Procedure Act requires federal agencies to provide substantial justification for reversing previous determinations, particularly those based on scientific evidence.
“Courts have established that agencies can’t simply change course without adequate explanation,” said Jody Freeman, director of the Harvard Law School Environmental and Energy Law Program. “They would need to demonstrate either that the underlying science has changed or that there were legal errors in the original determination.”
The scientific consensus on climate change has only strengthened since 2009, making a science-based challenge difficult. The most recent National Climate Assessment, released in 2023, reinforced findings about the risks posed by greenhouse gas emissions and climate change impacts.
Massachusetts Attorney General Andrea Campbell, whose state was the lead plaintiff in the 2007 Supreme Court case Massachusetts v. EPA that led to the endangerment finding, has indicated her office would challenge any rescission attempt. “The science is clear that climate change poses real risks to public health and our economy,” Campbell said in a recent interview. “We would vigorously defend the legal foundations that protect Massachusetts residents.”
The 2007 Massachusetts v. EPA decision requires EPA to make an endangerment determination based on scientific evidence. The Supreme Court ruled 5-4 that EPA had the authority to regulate greenhouse gas emissions from vehicles if the agency determined they endangered public health or welfare.
Environmental groups have also signaled they would mount immediate legal challenges to any rescission attempt. “The endangerment finding is based on overwhelming scientific evidence that has only grown stronger over the past decade,” said David Doniger, senior strategic director of the Natural Resources Defense Council’s Climate and Clean Energy Program.
The procedural requirements for rescinding the finding would likely take considerable time. Under federal rulemaking procedures, EPA would need to publish a proposed rule, allow for public comment, and provide detailed scientific and legal justification for the change.
“This isn’t something that could happen overnight,” said Ann Carlson, co-director of the Emmett Institute on Climate Change and the Environment at UCLA School of Law. “The rulemaking process, combined with inevitable litigation, would likely take years to resolve.”
Vehicle emission standards represent one of the most significant regulatory programs that depends on the endangerment finding. The current standards, which require automakers to achieve fleet-wide averages of about 40 miles per gallon by 2026, were estimated by EPA to provide $1.7 trillion in net benefits through 2050.
The automotive industry has invested billions of dollars in compliance with existing standards and has generally supported regulatory certainty. “Manufacturers have made substantial investments based on current regulatory frameworks,” said John Bozzella, president of the Alliance for Automotive Innovation.
Power plant regulations also rely on the endangerment finding. While the Supreme Court’s 2022 decision in West Virginia v. EPA limited certain approaches to regulating power plant emissions, it did not question EPA’s underlying authority to address greenhouse gas emissions from the sector.
State governments have increasingly filled gaps in federal climate policy, with 24 states plus the District of Columbia participating in regional carbon pricing programs or adopting clean energy standards. Many of these state programs operate independently of federal regulations but could face new challenges if federal standards were eliminated.
“States have become increasingly important players in climate policy,” said Barry Rabe, a professor at the University of Michigan’s Ford School of Public Policy. “But federal standards still play a crucial coordination role.”
Legal precedent suggests courts would scrutinize any rescission attempt carefully. Federal judges have consistently required agencies to provide substantial justification when reversing previous scientific determinations, particularly in cases involving public health and environmental protection.
The controversy ultimately traces back to the 2007 Supreme Court decision in Massachusetts v. EPA, which established EPA’s obligation to make science-based determinations about greenhouse gas emissions. That case arose from a coalition of states, cities, and environmental groups challenging EPA’s refusal to regulate vehicle emissions.
Any future legal challenge to a rescission would likely involve many of the same parties, setting up a potentially lengthy court battle over the scope of federal climate authority and the role of scientific evidence in regulatory decision-making.