Attorney General Phil Weiser vowed to sue the federal government to restore vehicle regulations the Environmental Protection Agency says added $2,400 to the cost of new cars. The lawsuit would be his 52nd federal legal action in the past year as he campaigns for governor on an affordability platform.
On February 12, EPA Administrator Lee Zeldin rescinded the 2009 “endangerment finding” that greenhouse gases endanger public health. The finding provided legal authority for federal regulation of carbon dioxide and methane emissions from motor vehicles under the Clean Air Act. EPA estimates the rescission eliminates $1.3 trillion in regulatory costs through 2055, including $1.1 trillion from reduced vehicle manufacturing requirements and $200 billion from avoided electric vehicle equipment costs.
The action removes all federal greenhouse gas emission standards for vehicles from model years 2012 through 2027 and beyond. It eliminates requirements that automakers measure, report, and certify compliance with federal greenhouse gas limits. It also removes “off-cycle credits” that rewarded manufacturers for adding features like automatic start-stop engine systems, which now appear in 60% of new vehicles despite causing acceleration lag drivers widely dislike.
Weiser called the EPA action “the largest deregulatory decision in American history” with “no legal or scientific justification.” He promised to sue to restore the endangerment finding, claiming Colorado experiences “record drought, catastrophic wildfires, ever-increasing heatwaves” requiring continued federal greenhouse gas regulation.
The Attorney General is running for governor against Senator Michael Bennet in Colorado’s June Democratic primary. His campaign focuses on lowering costs for Colorado families. A lawsuit to restore federal regulations EPA calculates increased vehicle prices by $2,400 would use Colorado taxpayer money to fight for higher consumer costs. Colorado Attorney General operations cost approximately $45 million annually. Weiser has filed 51 federal lawsuits against the Trump administration since January 2025.
The EPA rescission affects only greenhouse gas regulations. The agency explicitly stated the action “does not affect regulations on criteria pollutants and air toxics.” Criteria pollutants include nitrogen oxides, carbon monoxide, hydrocarbons, and particulate matter—emissions that cause smog and respiratory illness.
This distinction matters because vehicle “deletion”—removing emissions control equipment—remains illegal under the Clean Air Act. Diesel truck owners remove diesel particulate filters and exhaust gas recirculation systems. Gasoline vehicle owners remove catalytic converters and reprogram engine computers to bypass oxygen sensors. Both modifications eliminate controls on criteria pollutants, not greenhouse gases.
EPA investigations found emissions controls removed from over 500,000 diesel pickup trucks. Deleted diesel trucks emit 30 to 300 times more nitrogen oxides and 15 to 40 times more particulate matter than compliant vehicles. Deleted gasoline vehicles produce three to five times more criteria pollutants.
The Biden EPA pursued aggressive enforcement from 2020 through 2024, resolving 170 civil cases with $55.5 million in penalties and 17 criminal cases resulting in $5.6 million in fines and 54 months of collective prison time. Civil penalties under the Clean Air Act reach $5,580 per non-compliant part per day. Individual vehicles face penalties exceeding $50,000.
On January 21, the Justice Department announced it will no longer pursue criminal charges for tampering with emissions equipment. EPA Administrator Zeldin stated that stopping defeat devices is “not an EPA priority.” But the DOJ confirmed it “will still pursue civil enforcement for these violations when appropriate.” Criminal prosecution ended. Civil penalties remain.
Colorado requires emissions testing in Boulder, Broomfield, Denver, Douglas, and Jefferson counties, plus portions of Adams, Arapahoe, Larimer, and Weld. The state tests for criteria pollutants—hydrocarbons, carbon monoxide, and smoke opacity. Tests cost $25 biennially.
The EPA’s greenhouse gas rescission does not affect Colorado’s emissions testing program. Colorado tests measure criteria pollutants, not greenhouse gases. Vehicles with deleted emissions equipment fail Colorado testing because deletion removes hardware controlling the pollutants Colorado measures. Enhanced emissions testing identifies disabled or removed emissions controls. Vehicles cannot be registered until violations are corrected, typically costing $1,500 to $5,000 for repairs.
Federal law still prohibits tampering with emissions control systems designed to reduce criteria pollutants. The EPA rescission removed federal authority over greenhouse gases while preserving authority over traditional air pollutants. Vehicle owners who delete emission`ns equipment violate federal law and face civil penalties. Colorado continues testing for the pollutants deletion increases.
Weiser’s promised lawsuit to restore greenhouse gas regulations will cost Colorado taxpayers while he campaigns for governor on reducing costs. Colorado voters will determine in June whether they prefer an Attorney General who sues to restore vehicle costs or a Senator who legislates restrictions on federal enforcement.
Support Independent Local Journalism — High Country Advocate was created as a real alternative to regional media that too often silences dissenting voices while taking sides in the political struggle. Producing in-depth, unflinching reporting like this series and others is expensive: servers, editing, research time, and legal review all add up quickly. If these articles have informed you or given you new perspective, please consider supporting HCA with a paid subscription — every subscriber helps keep this reporting strong and independent. 