Attorney General Phil Weiser joins lawsuit challenging Trump administration’s attack on Colorado’s Clean Car Program

June 12, 2025 (DENVER) – Attorney General Phil Weiser today joined a coalition of attorneys general in filing a lawsuit challenging the unprecedented and unlawful use of the Congressional Review Act to reject the federal Clean Air Act waivers that allow California to adopt more stringent vehicle emissions standards for cars and medium and heavy-duty trucks. As allowed by federal law, Colorado has adopted California’s standards.

The Congressional Review Act allows Congress to overturn a narrow class of federal agency rules. California’s waivers have never been subject to the Act, and in the past the EPA has agreed that the waivers are not reviewable under the Act. In a naked attempt to circumvent the normal process for reviewing waivers, the current EPA changed course and submitted the waivers to Congress for disapproval. The actions taken here contradict the non-partisan Government Accountability Office and Senate Parliamentarian. Both determined that the Congressional Review Act’s process to disapprove federal regulations does not apply to these waivers.

“The Trump administration’s attack on clean air is breathtaking. Rolling back the federal Clean Air Act waivers through the illegal use of the Congressional Review Act is an assault on the authority of states, like Colorado, to adopt stronger tailpipe pollution limits than those set by the federal government,” said Attorney General Weiser. “We’re in court to defend Colorado’s cost-effective clean car program, which was implemented to improve air quality, reduce harmful ozone pollution, and increase choices that Coloradans have when purchasing an electric vehicle.”

Transportation is the leading source of greenhouse gas emissions in the country, and cars and trucks account for 80% of those transportation emissions. The Clean Air Act requires the EPA to set federal emission standards for air pollutants from new motor vehicles that endanger public health or welfare. The law allows California to adopt more stringent emission requirements independently from EPA’s regulations because California faces severe air pollution challenges and had vehicle emissions standards before the passage of the federal Clean Air Act. The Act requires the EPA to approve waivers for California’s rules absent certain, limited circumstances not present here. Once EPA grants California a waiver, other states may adopt California’s standards without a waiver of their own.

Colorado adopted California standards to help the state achieve its greenhouse gas reduction goals, reduce ozone precursor emissions, and reduce harmful direct exposure to pollutants from medium and heavy-duty trucks. The Colorado Air Quality Control Commission adopted these standards to provide cost-effective emission reduction benefits needed to address Colorado air quality and climate change goals.

The Colorado Clean Cars standards adopted in October 2023 direct vehicle manufacturers to make and sell more electric vehicles starting with model year 2027 and increasing each year through 2032 so that 82% of all vehicles sold in the state are electric. The standard also requires new conventional cars and passenger trucks to produce less air pollution and will help improve air quality for all Coloradans.

Likewise, Colorado’s adoption of California’s Advanced Clean Truck standards requires medium- and heavy-duty truck manufacturers to sell an increasing percentage of zero-emission vehicles from model 2027 and beyond, Colorado has also adopted California’s Heavy-Duty Low Nitrogen Oxides rule requiring heavy-duty truck manufacturers to make cleaner heavy-duty trucks for sale or lease in Colorado starting in 2027. When mixed with other air pollutants and heat and sunlight, nitrogen oxides can form harmful ground-level ozone, an ongoing environmental challenge for Colorado’s front range.

The complaint filed today alleges that the attempt to invalidate California’s waivers violated constitutional principles of federalism and separation of powers, the Take Care Clause, and multiple federal statutes including the Congressional Review Act and Administrative Procedure Act. The complaint asks the court to declare the resolutions unlawful and require the administration to implement the Clean Air Act consistent with the granted waivers.

Attorney General Weiser joins California Attorney General Rob Bonta and the attorneys general of Delaware, Massachusetts, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, and Washington in filing the lawsuit.

Read the states’ lawsuit California v. EPA (PDF).

###

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