Denver Joins 26 States and Localities in Federal Lawsuit Against NHTSA Over CAFE Standards
On October 2, 2026, the City and County of Denver joined a coalition of 26 other states, counties, and cities to file a lawsuit in the U.S. Court of Appeals for the First Circuit against the National Highway Traffic Safety Administration (NHTSA). The legal action challenges a final rule issued by the agency that weakens corporate average fuel economy (CAFE) standards for new passenger cars and light trucks over the next five years. According to denvergov.org, the challenged rule requires less fuel efficiency than what the U.S. fleet actually achieved in 2021.
Coalition Alleges NHTSA Rule Violates Federal Law
The coalition alleges in court filings that the NHTSA rule is arbitrary, capricious, and violates both the Administrative Procedure Act and the Energy Policy and Conservation Act of 1975. Under federal law, NHTSA must establish fuel economy standards at their maximum feasible level, factoring in technological feasibility, economic practicability, and the need to conserve energy. Colorado Attorney General Phil Weiser noted in a statement reported by coag.gov that the federal backsliding forces lower efficiency targets than past industry benchmarks. The lawsuit asserts that the agency misinterprets its statutory authority by excluding existing electric vehicles from its baseline fleet analysis.
Economic and Environmental Impacts Cited by Coalition Leaders
City and state leaders argue that weakening fuel efficiency targets harms consumers and increases household expenses. Denver Mayor Mike Johnston stated that gas prices are already elevated and that the regulatory rollbacks add financial strain on drivers. According to denvergov.org, the NHTSA analysis dismisses nearly $220 billion in potential fuel savings for drivers at the pump while omitting hundreds of billions of dollars in projected climate change damages. The lawsuit also points out that the federal rule will terminate the CAFE credit trading program in 2028, impacting electric vehicle industries and domestic manufacturing employment.
States and Cities Join Lawsuit Against Federal Action
Attorney General Phil Weiser and Mayor Mike Johnston joined a broad coalition of attorneys general and municipal governments challenging the federal action. As reported by coag.gov, the participating states and cities include California, Arizona, Connecticut, Delaware, Hawai‘i, Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New Mexico, New York, North Carolina, Oregon, Rhode Island, Vermont, Washington, Wisconsin, the District of Columbia, the City of Chicago, the City of New York, and the City and County of San Francisco. This filing marks the second lawsuit Denver joined this week to protect against attacks on clean air standards.
Frequently Asked Questions About the CAFE Standards Lawsuit
Which court is hearing the lawsuit against NHTSA?
The coalition filed the lawsuit in the U.S. Court of Appeals for the First Circuit on October 2, 2026, challenging the National Highway Traffic Safety Administration’s final rule.
What specific federal legislation does the coalition claim NHTSA violated?
The lawsuit alleges violations of the Administrative Procedure Act and the Energy Policy and Conservation Act of 1975, which requires maximum feasible fuel economy standards.
How does the new rule affect the electric vehicle market?
According to court filings from denvergov.org and coag.gov, the final rule ignores millions of existing electric vehicles in its fleet baseline and will end the CAFE credit trading program in 2028.
The Energy Policy and Conservation Act of 1975 established the original statutory framework requiring federal regulators to set vehicle efficiency standards that reflect technological feasibility and energy conservation.
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