Huron Portland Cement Co. v. City of Detroit

Justices Douglas and Frankfurter strongly disagreed with the majority opinion. They argued that, "[t]he requirements of the Detroit smoke ordinance are squarely in conflict with the federal statute." The dissenters agreed that there were many areas in which local regulations might be added to federal ones. Speed limits, traffic regulations, or rules for using a dock might all exist alongside of federal laws for inspecting and licensing boats. But, wrote Douglas, in those cases:

. . . we would have local laws not at war with the federal license, but complementary to it . . . This case [on the other hand] . . . involves the collision between a local law and a federal law . . .