On June 11, 2025, EPA Administrator Zeldin proposed to repeal two regulations finalized by the Biden administration that limited pollution from fossil fuel-fired power plants: updates to the Mercury and Air Toxics Rule and the Carbon Pollution Standards. If finalized, these proposed repeals would allow emissions from power plants to increase.

The proposed repeal of GHG standards finds that the emissions from fossil-fuel fired plants “do not contribute significantly to dangerous air pollution” within the meaning of Clean Air Act section 111 despite the fact that fossil fuel-fired power plants are the largest stationary source of GHG pollution in the US. If EPA finalizes this portion of the proposal, and courts uphold it, the rule would eliminate all GHG emission standards for the power sector and preclude GHG regulations of other stationary sources under the Clean Air Act.

As an alternative to this significant contribution finding, the proposal also includes a repeal of most of the emission standards for power plants finalized by the Biden administration, arguing that the bases for the standards (i.e., carbon capture and sequestration and co-firing with natural gas) are not “adequately demonstrated” as required by the Clean Air Act.

In this legal analysis, we briefly summarize the proposal’s primary and alternative approaches and explore how EPA’s legal arguments depart from the agency’s past legal interpretations of section 111 — even those made by the first Trump administration. We highlight inconsistent arguments within the proposal and discuss the potential legal risks if EPA were to finalize a rule consistent with the proposal, including the agency’s failure to evaluate alternatives to fully rescinding the standards and reliance on policy justifications rather than the statutory criteria. We also explain how the arguments asserted by the proposal are similar to justifications rejected by the Supreme Court in Massachusetts v. EPA.