The State of Maryland conducted a survey following the 1973 gas shortage and determined that petroleum producers and refiners had given their own service stations preferential treatment with respect to gasoline distribution and pricing over independently owned retail service stations. To combat this, Maryland passed a statute that prohibited producers or refiners from operating retail service stations within the state. Out-of state oil producers and refiners operate approximately 5 percent of the state’s retail stations, but no oil is produced or refined in the state. Exxon Corp. (Exxon) (plaintiff) brought suit against the Governor of Maryland (defendant) on constitutional and statutory grounds, arguing that the Maryland law impermissibly discriminated against interstate commerce and was preempted by federal policy. Other oil companies filed similar lawsuits. The trial court held that the statute was invalid, but the Maryland Court of Appeals reversed. Exxon then appealed to the United States Supreme Court.