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A coalition of health and environmental groups filed a lawsuit against the Environmental Protection Agency (EPA) on Wednesday (February 18), challenging the agency's recent decision to rescind the 2009 "endangerment finding" that established greenhouse gases as threats to public health and welfare.

The legal challenge, filed in the U.S. Court of Appeals for the District of Columbia Circuit, argues that the EPA's action last week is unlawful and undermines the foundation for nearly all climate regulations under the Clean Air Act. The Obama-era finding has served as the legal basis for regulating greenhouse gas emissions from vehicles, power plants, and other pollution sources for the past 17 years.

The lawsuit was brought by numerous organizations including the American Public Health Association, American Lung Association, Alliance of Nurses for a Healthy Environment, and environmental groups such as the Center for Biological Diversity, Environmental Defense Fund, and Sierra Club. The suit names EPA Administrator Lee Zeldin and the EPA itself as defendants.

President Donald Trump celebrated the repeal as "the single largest deregulatory action in American history, by far," while Zeldin described the endangerment finding as "the Holy Grail of federal regulatory overreach." The administration claims the finding led to regulations that "strangled entire sectors of the United States economy."

The repeal eliminates all greenhouse gas emissions standards for cars and trucks and could lead to further rollbacks of climate regulations for power plants and oil and gas facilities. Clean vehicle standards established by the Biden administration were set to deliver significant cuts to U.S. carbon pollution while saving consumers money on fuel.

Environmental advocates point out that the EPA's own analysis found that eliminating vehicle standards will increase gas prices and force Americans to spend more on fuel.

Under the Clean Air Act, the EPA is legally required to limit emissions of any air pollutant that endangers public health or welfare. In 2007, the Supreme Court ruled in Massachusetts v. EPA that greenhouse gases qualify as air pollutants under the law and directed the EPA to determine if they pose a danger. The agency made that determination in 2009.

The lawsuit contends that evidence supporting the endangerment finding has only grown stronger since it was first approved, with rising global temperatures and increasing climate impacts affecting communities nationwide.