The EPA kicked off the week with the proposed Affordable Clean Energy (ACE) rule, which is meant to replace the Clean Power Plan (CPP). As expected and foreshadowed by its proposed changes to the legal rationale underpinning the CPP, the EPA will regulate only source emissions, not sector-wide emission reduction activities. The EPA claims this “best system of emissions reduction” is consistent with the Clean Air Act Section 111(d) authority and is both technically feasible and appropriate for coal-fired power plants.