Dahl v. Montana Copper Company was a case heard by the Supreme Court of the United States in 1912. The case involved a dispute between the Montana Copper Company and the Dahl family over the ownership of a mining claim in Montana. The Dahl family had been living on the land for several years and had made improvements to the property, while the Montana Copper Company had recently acquired the mineral rights to the land. The Supreme Court held that the Dahl family had acquired a valid possessory title to the land, and that the Montana Copper Company had no right to the land. The Court also held that the Dahl family was entitled to compensation for the improvements they had made to the land. The decision in Dahl v. Montana Copper Company established the principle that a person who has made improvements to land can acquire a possessory title to the land, even if they do not have legal title to the land. This principle has been applied in numerous cases since then, and is an important part of property law in the United States.

In the case of Dahl v. Montana Copper Company, Justice McReynolds delivered a dissenting opinion in which he argued that the majority's decision was wrong and should be overturned. He asserted that the state law allowing for an employer to terminate an employee without cause or notice violated due process as guaranteed by both federal and state constitutions. Furthermore, he argued that it was not within the power of a legislature to pass such laws because they were contrary to public policy and would lead to arbitrary decisions on behalf of employers with no recourse for employees who had been unjustly terminated. He concluded by stating his belief that this type of legislation could only be passed if there were some form of protection provided for workers against wrongful termination, otherwise it would violate their right to due process under both federal and state constitutions.