type: timeline_event
Colorado Attorney General Phil Weiser and a coalition of environmental groups including the National Parks Conservation Association and the Sierra Club (represented by Earthjustice) filed separate petitions in the U.S. Court of Appeals for the Tenth Circuit in early March 2026, challenging the Trump EPA's January 26 rejection of Colorado's state implementation plan for regional haze.
Colorado's plan — which had the support of utilities, industry, local governments, and environmental groups alike — included requirements for coal plant retirements and emission limits on industrial sources designed to improve visibility in national parks including Rocky Mountain National Park. The EPA rejected the plan, claiming the state had failed to provide "necessary assurances" that it did not violate federal and state takings law — a rationale that legal observers and the petitioners described as pretextual and legally baseless.
Earthjustice described the EPA action as "an illegal effort to prop up coal." National Parks Conservation Association Colorado senior program manager Tracy Coppola stated: "Colorado chose clean air. The EPA chose pollution."
The Colorado case was part of a broader pattern of the Trump EPA — led by EPA Administrator Lee Zeldin — systematically rejecting state-level environmental protections, rolling back the 2009 Endangerment Finding, eliminating vehicle emissions standards, and unwinding decades of Clean Air Act implementation. In each instance, the agency was using administrative procedures to protect fossil fuel industries from regulatory obligations that had already been agreed upon, often overriding state plans that had been developed over years of stakeholder consensus.