The U.S. Supreme Court case, Purcell et al., Constituting the Public Service Commission of Maryland, et al. v. United States et al., 1941 dealt with a conflict between state and federal jurisdiction over interstate commerce regulations. The Public Service Commission of Maryland had ordered Baltimore Transit Company to reduce its fares for intrastate passengers while maintaining higher rates for those traveling interstate routes in order to subsidize local service costs. However, this was challenged by the Interstate Commerce Commission (ICC) which argued that such an arrangement violated federal laws against discriminatory pricing practices in interstate commerce under the Interstate Commerce Act. The Supreme Court ruled in favor of ICC stating that it held exclusive authority over regulating rates for both intrastate and interstate travel when they are part of a through route or joint fare system involving more than one state. This decision affirmed the supremacy clause of Constitution where Federal law takes precedence over State law when there is any conflict between them on matters related to regulation of inter-state trade or commerce.

In the dissenting opinion for Purcell et al., Constituting The Public Service Commission of Maryland, et al. v. United States et al., Justice Frank Murphy argued that the majority's decision to uphold a federal law regulating interstate bus lines was an overreach of federal power and infringed upon states' rights. He contended that while Congress has authority over interstate commerce, it does not have unlimited power to regulate all aspects of businesses involved in such commerce. In his view, this case represented a situation where state regulation should prevail because buses operate within state boundaries most of the time despite being part of an interstate system. Furthermore, he expressed concern about potential negative impacts on local communities due to lack of consideration for their specific needs and conditions under broad federal regulations.