Attorney General Phil Weiser sues over Trump EPA rule that weakens regulation of highly potent greenhouse gas

July 21, 2026 (DENVER) – Attorney General Phil Weiser today joined a coalition of 19 attorneys general in filing a lawsuit against the U.S. Environmental Protection Agency, challenging its rule that would weaken regulations designed to phase out the use of hydrofluorocarbons in commercial equipment.

Hydrofluorocarbons, or HFCs, are super pollutants used in refrigeration and cooling systems that are up to 10,000 times more potent than the equivalent amount of carbon dioxide. They are among the fastest growing source of greenhouse gas emissions both in the United States and around the world. The rule rolls back some of the existing deadlines for industry to move from using HFCs as refrigerant gases to climate friendlier refrigerants. This undermines EPA’s current regulations under federal law, which are designed to phase out HFCs by approximately 85% by 2036.

In the petition filed today in the U.S. Circuit Court of Appeals for the District of Columbia, the coalition of states asks the court to review EPA’s new rule because it is contrary to law and the agency failed to justify its change in position.

“If allowed to move forward, the EPA rule will increase HFC emissions, disrupt the marketplace, harm consumers, and accelerate the damage already threatening our planet from climate change,” said Attorney General Weiser. “Leading and responsible companies are pushing for and ready for this transition to climate friendlier cooling systems. Undermining this change is illegal, irresponsible, and head scratching, as the law calling for this action was a bipartisan one signed by President Trump.”

In December 2020, President Trump signed the bipartisan American Innovation and Manufacturing Act into law. The law provides a framework through which the United States will phase out the production and consumption of HFCs by about 85% by 2036. That law limits production and imports of HFCs in the U.S. to declining amounts of historic baseline levels – 60 percent today, declining to 30 percent in 2029, and 15 percent in 2036. The law requires EPA to help industry transition to a lower supply of these gases by setting limits for sectors with more readily available alternatives to protect costs and supply for those sectors that will take longer to transition.

In 2023, the EPA adopted the Technology Transitions rule to facilitate industry’s transition away from HFCs and to alternative refrigerants when installing new equipment or replacing existing systems. For example, under the prior rule, new remote condensing units – typically used by supermarkets, cold storage warehouses, and conveniences stores – were limited to using refrigerants with 150 to 300 global warming potential, depending on the system, starting January 1, 2026. With EPA’s rollback, new remote condensing units could use refrigerants with 10 times greater global warming potential until January 1, 2032.

The lawsuit was led by California Attorney General Rob Bonta, Massachusetts Attorney General Andrea Campbell and Washington Attorney General Nick Brown. They were joined by the attorneys general of Colorado, Delaware, Hawai‘i, Illinois, Maine, Maryland, Michigan, Minnesota, Nevada, New Jersey, New York, Oregon, Rhode Island, Vermont, Wisconsin, the District of Columbia, and the City of New York.

Read a copy of the petition (PDF).

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Media Contact:
Lawrence Pacheco
Chief Communications Officer
(720) 508-6553 office
lawrence.pacheco@coag.gov