The Alliance for Clean Coal (Alliance) (plaintiff), a trade association whose members marketed and transported low-sulfur coal mined in the western United States, filed suit in federal court against Evan Bayh in his official capacity as governor of the State of Indiana, the Indiana Utility Regulatory Commission (the Commission), and others (defendants) alleging that Indiana’s Environmental Compliance Plans Act (ECPA) violated the federal Commerce Clause by favoring coal produced in Indiana at the expense of coal produced in the western United States. The ECPA was enacted in response to 1970 amendments to the Clean Air Act (CAA) which required coal-fired generating plants to significantly reduce sulfur dioxide emissions. Pursuant to the CAA amendments, the plants could do so by using low-sulfur coal commonly found in the western states or by installing devices to scrub sulfur dioxide emissions before they reached the atmosphere in the high-sulfur states like Indiana. Consequently, low-sulfur states enjoyed a competitive advantage over high-sulfur states. The district court found that the ECPA intended to promote Indiana coal at the expense of low-sulfur coal, thereby unconstitutionally burdening interstate commerce. The defendants appealed.