In this action, EPA is supplementing its proposal to repeal all greenhouse gas (GHG) emission standards for fossil fuel-fired electric generating units (EGUs) to effectuate the best reading of Clean Air Act (CAA) section 111. We propose that CAA section 111 does not authorize the EPA to regulate emissions from power plants in response to global climate change concerns. For the multiple and independent reasons described herein, this additional rationale would also require rescinding the Administrator's contrary findings and determinations in 2015 and repealing all associated 2015 and 2024 GHG standards for the fossil fuel-fired EGU source category. In a separate action published concurrently with this supplemental notice, the EPA is finalizing the repeal of certain 2024 GHG standards for the fossil fuel-fired EGU source category on distinct legal and technical grounds. We are not reopening that final rule. Nor are we soliciting further comment on those issues through this supplemental notice, except to the extent that commenters believe the final rule bears on the distinct questions of statutory authority addressed herein. Comments must be received on or before 2 November 2026. POC is Ms. Lisa Thompson, tele: (919) 541-5158 and email: thompson.lisa@epa.gov. (Federal Register 17 September 2026 [Rule] Pages 59002-59046)