The Secretary v. McGarrahan was a case heard by the United States Supreme Court in 1869. The case involved a dispute between the Secretary of the Interior and a man named McGarrahan, who had purchased a mining claim in California. The Secretary argued that the claim was invalid because it had been purchased from a Native American tribe, and that the tribe had no right to sell the land. McGarrahan argued that the tribe had the right to sell the land, and that he had a valid claim to it. The Supreme Court ultimately sided with McGarrahan, ruling that the tribe had the right to sell the land, and that McGarrahan had a valid claim to it. The Court held that the tribe had the right to sell the land because it was their property, and that the federal government had no right to interfere with the sale. The Court also held that the sale was valid because it was made in good faith, and that McGarrahan had a valid claim to the land. The decision in The Secretary v. McGarrahan was an important one, as it established that Native American tribes had the right to sell their land, and that the federal government could not interfere with such sales. The decision also established that individuals who purchased land from Native American tribes had valid claims to the land, and that the federal government could not invalidate such claims.

In the case of The Secretary v. McGarrahan, the Supreme Court was tasked with deciding whether a federal law that allowed for the sale of public lands in California applied to those who had already settled on them prior to its passage. Justice Field wrote a dissenting opinion arguing that Congress did not have authority under the Constitution to pass such a law and thus it should be declared unconstitutional. He argued that if Congress could pass laws retroactively affecting private property rights, then no one would be safe from arbitrary government action and their fundamental right to own land would be violated. Furthermore, he noted that this particular law was passed without any compensation being offered for those who had already settled on these lands and thus they were deprived of their property without due process or just compensation as required by both state constitutions and the Fifth Amendment of the U.S Constitution.