In the late 1930s, Continental Ore Company (Continental Ore) (plaintiff) entered the vanadium trade. Vanadium was a metal used in steel alloys. At the time, Vanadium Corporation of America (VCA) (defendant) and Union Carbide and Carbon Corporation (Carbide) (defendant) controlled over 90 percent of the United States vanadium market. In 1943, to allocate wartime resources, the Canadian government put a subsidiary of Carbide, Electro Metallurgical Company of Canada, Ltd. (Electro Met) (defendant), in charge of purchasing and allocating all vanadium in Canada. With this power, Electro Met eliminated Continental Ore from the Canadian market and gave Continental’s former Canadian market share to Carbide and VCA. Continental Ore sued VCA, Carbide, Electro Met, and other Carbide subsidiaries (defendants) in district court. Continental Ore claimed that VCA and Carbide had conspired to monopolize the vanadium trade in the United States. Continental Ore also claimed VCA and Carbide conspired to use Electro Met’s powers to exclude Continental Ore from the Canadian vanadium market. The district court refused to hear evidence on allegations related to the Canadian market. The district court held Electro Met’s actions were authorized by the Canadian government and outside the Sherman Act’s scope. The court of appeals affirmed, concluding that even if Electro Met acted to further a domestic antitrust conspiracy by Carbide and VCA, Electro Met nonetheless acted with the authority of the Canadian government. Continental Ore appealed to the United States Supreme Court.