ELR Citation: 55 ELR 20029
No(s). 23-9565 (10th Cir. Mar 4, 2025)

The Tenth Circuit denied environmental groups' petition to review an EPA rule that partially approved Colorado's SIP to reduce ozone pollution. The groups sought vacatur of the approval, arguing the Agency violated the CAA by approving the reasonable further progress and motor vehicle emissions budget components in 2022 to lower ozone levels after the state missed its 2021 deadline for meeting national ozone standards; that Colorado improperly included state-only emissions reductions in its reasonable further progress calculations; and that the SIP violated the CAA's anti-backsliding provision. The court found EPA acted lawfully in approving the reasonable further progress and motor vehicle emissions budget components, and that those approvals neither impermissibly depended on emissions reductions from state-only measures nor contravened the anti-backsliding provision. It denied the petition for review.