The EPA intends to revisit its previous actions finalizing the disapproval or partial disapproval of state implementation plans (SIPs) and finalizing federal implementation plans (FIPs) addressing states’ interstate transport obligations under the 2015 ozone national ambient air quality standards (NAAQS). Following numerous challenges to EPA’s past transport actions for the 2015 ozone NAAQS, multiple federal courts have stayed EPA’s actions as to nearly half of states with disapproved 2015 ozone transport SIPs. Consistent with the EPA Administrator’s regulatory agenda announcement in March 2025, this action intends to invoke the principles of cooperative federalism while accomplishing EPA’s core mission of protecting the environment.