In the 1896 case of Forsyth v. Hammond, the U.S. Supreme Court dealt with a dispute over land ownership in California that originated during the Mexican-American War. The plaintiff, Thomas Forsyth, claimed he had purchased a plot of land from Pio Pico (the last governor of Alta California under Mexican rule) before American forces took control of the region in 1846. However, after this transition to American governance occurred, another man named George Hammond received a patent for this same piece of property from U.S authorities based on an older Spanish grant dating back to 1821. The main issue was whether or not Forsyth's purchase could be considered valid since it happened during wartime when political authority was uncertain and changing hands rapidly between Mexico and America. Ultimately, the court ruled against Forsyth because his claim relied heavily on recognizing Pico's authority at a time when it was questionable due to ongoing military conflict. Furthermore, they found that even if Pico did have legitimate power at that moment in history; he still would not have been able to sell public lands without approval from Mexico’s Departmental Assembly which never occurred according to available records.

The dissenting opinion in the Forsyth v. Hammond case argued that the majority's decision was incorrect because it failed to consider important aspects of property law and rights. The dissent emphasized that a person who purchases land with notice of an existing lease has their rights subject to such lease, even if they were not party to its creation or execution. They contended that Mr. Hammond had no right to eject Mrs. Forsyth from her home as she held a valid lease at the time he purchased the property, which should have been respected under established legal principles governing real estate transactions and ownership rights.