On November 1, 2006, the Supreme Court will hear oral argument in Environmental Defense v. Duke Energy Corp. (“Duke Energy”). Duke Energy is one case in the Environmental Protection Agency’s (“EPA” or “the agency”) broad “coal-fired power plant enforcement initiative.” Launched in 1999, this initiative is an attempt by EPA to enforce the Clean Air Act’s (“the Act”) new source review (“NSR”) program in a novel way, one disconnected from over twenty years of agency practice and from the practical realities of operating a power plant. Duke Energy presents the Court with the opportunity to resolve definitively legal issues surrounding the NSR program, as well as to vindicate Congress’ intent to balance environmental and economic concerns in a way that maintains air quality while allowing industrial facilities to achieve emissions reductions in a cost-effective manner, rather than imposing inefficient unit-specific controls on every source.