In the 1902 case of Ambrosini v. United States, the U.S Supreme Court dealt with a dispute over land ownership in California. The plaintiff, Ambrosini, claimed that he had acquired title to certain lands through preemption rights under federal law. However, these lands were part of a Mexican land grant confirmed by Congress and patented to one Pioche in 1870. The court held that once Congress confirms such a grant and issues patent for it, all public lands within its boundaries are segregated from public domain; they can no longer be preempted or otherwise disposed of by the government until after judicial determination excluding them from operation of confirmation act and restoration to public domain by proper authority. Therefore, even if there was any error in including these particular lands within boundaries described in patent issued on confirmation proceedings (which wasn't proven), this wouldn't have affected validity of patent or given anyone right to enter upon property under pretense of preempting it as part thereof before exclusion thereof from operation of act confirming claim thereto.

In the dissenting opinion for Ambrosini v. United States, it was argued that the court erred in its decision to uphold a conviction based on evidence obtained through an allegedly illegal search and seizure. The dissenting justices contended that the Fourth Amendment's protections against unreasonable searches and seizures should have been applied more rigorously in this case. They believed that law enforcement officials had overstepped their bounds by conducting a warrantless search of Ambrosini's property, thereby violating his constitutional rights. Furthermore, they disagreed with the majority's interpretation of what constitutes "probable cause" for issuing a search warrant, arguing instead for stricter standards to prevent potential abuses of power by law enforcement agencies.