On April 6, the U.S. Environmental Protection Agency (EPA) published in the Federal Register a proposed rule that, if finalized, would establish a federal implementation plan (FIP) to address regional ozone transport under the Clean Air Act (CAA). The proposed rule is noteworthy based on the numerous adjustments it makes to existing nitrogen oxides (NOx) emissions budgets for a number of states, including Pennsylvania, as well as marking the first time that the EPA has used the regional ozone transport provision under the CAA to regulate sources other than electricity generating units (EGUs).