In the Armstrong v. United States case of 1900, the U.S Supreme Court ruled on a dispute involving land ownership in California. The plaintiff, Armstrong, claimed that he had purchased lands from Mexican citizens who held valid titles granted by the Mexican government before California was ceded to America following the Treaty of Guadalupe Hidalgo in 1848. However, these claims were rejected by both lower courts and later by the Supreme Court because they failed to meet certain requirements set forth under American law for validating such land grants made under foreign governments prior to their acquisition by America. Specifically, it was required that any claim based on such a grant should have been presented to and confirmed by an American board of land commissioners within two years after its establishment in 1851 as per an act passed in March 3rd, 1851 (Act). Since this requirement wasn't met with respect to Armstrong's purchase deeds dated back between late-1860s and early-1870s i.e., long after expiry of said two-year period post-establishment of said commission; his claims were deemed invalid leading up-to affirmation thereof via this judgement.

In the dissenting opinion for Armstrong v. United States, Justice Harlan argued that the majority's decision was a misinterpretation of the law and an infringement on individual rights. He contended that under U.S. law, private property could not be taken without just compensation - even in times of war or rebellion - unless it was used to directly aid in insurrection against the government. In this case, he believed there wasn't sufficient evidence to prove that Armstrong’s cotton had been used for such purposes; hence its seizure by military authorities during Civil War was unlawful and unconstitutional. Furthermore, he emphasized that Congress did not have authority to retroactively validate such seizures if they were originally illegal according to Fifth Amendment protections against uncompensated takings of private property by government action.