In the United States v. Post case of 1892, the Supreme Court ruled on a dispute over land ownership in Michigan. The defendant, Post, claimed that he had purchased his property from Native Americans who had received it through a treaty with the U.S government. However, this was disputed by the plaintiff - the U.S government - which argued that under federal law only Congress could approve such sales and no approval had been given for this transaction. The court sided with the government's argument and held that any sale of tribal lands to private individuals without congressional approval is invalid because tribes do not have full title to their reservation lands; they hold them "in trust" at pleasure of Congress which has ultimate authority over these territories due to its plenary power doctrine (absolute power) regarding Indian affairs.

In the dissenting opinion for United States v. Post, Justice Brewer argued that the government did not have a valid claim to land in question because it had failed to establish any actual possession or use of the property. He contended that mere discovery and exploration by Lewis and Clark did not constitute occupation or possession under international law standards of the time. Furthermore, he pointed out inconsistencies in how such claims were treated depending on whether they involved lands occupied by civilized nations versus those inhabited by indigenous peoples. In his view, this case was an example of overreach on part of federal government trying to assert control over lands without having established clear legal rights thereto.