In the United States Supreme Court case of The United States v. The Heirs of Francisco de Haro, Deceased, the court was asked to determine whether or not a land grant made by Mexico in 1846 was valid and enforceable under U.S. law after California became part of the United States following its annexation in 1850. At issue were two conflicting claims: one from an individual who had purchased a portion of the land prior to California's annexation and another from heirs claiming title through their ancestor's original Mexican land grant issued before that time. Ultimately, the court found that while it could not recognize any rights acquired under Mexican law after California joined with America, it did find that those rights which existed at such time should be respected and enforced as if they had been granted by American authorities themselves; thus upholding both parties' respective claims over portions of this disputed property according to their pre-existing titles established during Mexico's sovereignty over what is now known as California state territory.

The United States brought a case against the Heirs of Francisco de Haro, deceased, claiming that they were in possession of land which had been granted to them by Mexico before California became part of the United States. The Supreme Court ruled in favor of the Heirs and held that their title was valid under Mexican law and could not be taken away from them without due process. Justice Grier dissented from this opinion, arguing that since California was now part of the United States it should be subject to U.S. laws rather than those established by Mexico prior to its annexation. Furthermore, he argued that any claims made under Mexican law would have no legal standing as they did not recognize private property rights at all; thus any grant issued by Mexico would be invalidated upon becoming part of the US territory regardless if it had been properly executed or not according to Mexican law.