Colorado is taking its coal fight to a higher court, asking the U.S. Court of Appeals for the Tenth Circuit to overturn the Environmental Protection Agency’s rejection of the state’s regional haze plan. At the heart of the case is whether federal clean air rules can effectively sideline a coal unit by turning a planned retirement into a binding federal obligation, and what that means for Colorado Springs Utilities’ Nixon Unit 1.
State Sues After EPA Disapproval
The Colorado attorney general filed a petition for review in the Tenth Circuit on March 4, challenging EPA’s decision to disapprove the state’s 2022 regional haze State Implementation Plan. According to the Colorado Attorney General, the state argues that EPA swapped out the statute for its own policy preferences and improperly tossed out the entire plan instead of fixing specific pieces.
What EPA Said And The Takings Concern
EPA’s final action, published in the Federal Register, concluded that Colorado had not provided the “necessary assurances” that plant closures written into the plan without the owner’s firm consent would avoid violating federal or state takings law. The agency warned that treating a forced shutdown as part of an approved SIP could raise Fifth Amendment issues tied to property rights. EPA also highlighted grid reliability concerns linked to several scheduled retirements as part of its explanation. See EPA’s Federal Register notice for the agency’s detailed legal reasoning and analysis.
Why Nixon Unit 1 Matters
Colorado’s haze plan set a retirement date of the end of 2029 for Colorado Springs Utilities’ Ray D. Nixon Unit 1, a deadline that utility officials later told regulators they could not realistically meet. Local reporting and utility statements show Colorado Springs Utilities flagged both cost and reliability problems if Nixon had to shut down on that schedule, and CEO Travas Deal has criticized the sped-up timeline as rushed and impractical. See coverage in The Denver Gazette for more on the utility’s position and the state’s compromise talks.
Environmental Groups Push Back
Conservation groups are not exactly cheering the EPA’s call either. The National Parks Conservation Association and Sierra Club, represented by Earthjustice, quickly filed their own petition that argues EPA’s disapproval undercuts long-standing efforts to clear up haze in national parks. In a statement reported by Earthjustice, advocates said Colorado’s plan would have delivered meaningful emissions cuts for places like Rocky Mountain National Park and warned that walking it back sets a troubling precedent.
What The Court Will Weigh
The Tenth Circuit now has to referee competing legal theories. One core question is whether EPA was right to insist on stronger assurances to avoid a potential taking when a retirement is written into a SIP. Another is how far a state can lean on voluntary retirement commitments and still have those promises treated as federally enforceable requirements. Legal trackers note that Colorado’s petition is docketed as Colorado v. EPA, No. 26-09515, and that Colorado Springs Utilities has been allowed to intervene in the case. See the Harvard Environmental and Energy Law Program tracker for the case posture and filings.
Grid Reliability And Federal Politics
All of this is playing out against a backdrop of reliability worries and political tug of war over coal’s future in Colorado. The U.S. Department of Energy issued an emergency order late in 2025 to keep a separate Colorado coal unit available during winter reliability concerns, while state legislators have been wrangling over bills that would give utilities more time to swap out coal plants. The DOE action and those legislative negotiations help explain why reliability arguments now sit front and center in the litigation; see the U.S. Department of Energy and local reporting at CPR News for additional background.
What To Watch Next
Court watchers say the Tenth Circuit’s decision could set a national template for how, or whether, states can fold voluntary coal plant retirements into federally enforceable air plans. Colorado and the environmental petitioners are pitching the case as a key test of how federal and state tools can be used to clean up visibility in parks, while EPA and utilities emphasize statutory boundaries and the need to keep the lights on. EPA’s response to the petitions is expected this summer, and the precise briefing schedule will play out on the Tenth Circuit docket, where filings will show how each side frames this high-stakes coal showdown.
