In the case of AINSA v. UNITED STATES in 1901, the Supreme Court was tasked with determining whether a land grant given by Spain to an individual before Mexico gained independence from Spain and subsequently ceded territory to the United States should be recognized under U.S law. The plaintiff, Ainsa, claimed ownership over certain lands in Arizona based on a Spanish land grant made to his ancestor prior to Mexican Independence. However, this claim had not been presented for confirmation until after Arizona became part of the United States following the Gadsden Purchase treaty between US and Mexico in 1854. The court ruled against Ainsa stating that he failed to assert his rights within a reasonable time frame as required by international law principles regarding changes of sovereignty over territories. Therefore, it held that such claims must be brought forward promptly when new sovereigns take control or they may be deemed abandoned or forfeited due to laches (unreasonable delay). This decision reinforced respect for territorial integrity while also emphasizing timely assertion of property rights during transitions of national authority.

In the dissenting opinion for AINSA v. UNITED STATES, Justice Harlan argued that the majority's decision was inconsistent with both international law and previous Supreme Court rulings. He contended that under international law, a nation has exclusive jurisdiction over its own territory, including any unappropriated public lands within its borders. Therefore, he believed that Spain had full authority to grant land rights in Arizona to Ainsa before it ceded the territory to the United States as part of the Treaty of Guadalupe Hidalgo in 1848. Furthermore, Justice Harlan pointed out that prior Supreme Court decisions had upheld similar Spanish land grants made before other territories were ceded to America. Thus, he concluded that these precedents should have been followed in this case too and therefore disagreed with his colleagues' ruling against Ainsa's claim.