In the United States Supreme Court case of The United States v. Mariano G. Vallejo, the issue was whether or not a Mexican land grant in California was valid under American law. Vallejo had received a large tract of land from Mexico prior to California becoming part of the US and he argued that his title should be respected by American courts as it had been recognized by Mexico before its cession to America. The US government disagreed and argued that since California became part of the Union, all titles were subject to review according to federal laws and regulations governing public lands in newly acquired territories. After considering both sides' arguments, the court ruled in favor of Vallejo's claim; they found that his title was valid because it predated any applicable federal laws regarding public lands in new states or territories and thus could not be invalidated on those grounds alone.

In the case of The United States v. Mariano G. Vallejo, the Supreme Court was asked to decide whether a Mexican land grant in California was valid under US law. Justice Curtis wrote a dissenting opinion arguing that Congress had not intended to invalidate such grants when it passed legislation governing public lands in California and that therefore they should be respected as valid titles by the courts. He argued further that if Congress wanted to invalidate these grants, then it would have done so explicitly rather than leaving them open for interpretation by the courts. Furthermore, he noted that since Mexico had been recognized as an independent nation at the time of its cession of California to America, any rights granted prior to this event were still legally binding on both countries and could not be overturned without explicit action from either government or through treaty provisions between them.