In the case of Juan M. Luco and Jose Leandero Luco v. The United States, two brothers from Cuba were appealing a decision made by the district court in Florida that denied them their freedom as they had been held as slaves since 1848. They argued that under Spanish law, which was still in effect when they arrived to Florida, slavery was illegal and thus their enslavement was unlawful. The Supreme Court ultimately ruled against them on the basis that while Spain may have abolished slavery within its own borders prior to 1821, it did not extend this protection to those living outside of its jurisdiction; therefore any laws abolishing slavery would not apply retroactively or be applicable beyond Spanish borders at the time of their arrival in 1848. As such, despite being illegally enslaved according to Spanish law at one point in time, these individuals could still be legally held as slaves due to US federal laws regarding slave ownership and interstate commerce between states with different legal statuses for persons of African descent during this period.

In the case of Juan M. Luco and Jose Leandero Luco v. The United States, the appellants argued that they were entitled to a patent for land in California which was granted to them by Mexico prior to its cession to the United States. The Supreme Court disagreed with this argument, holding that under Mexican law at the time of cession, no valid title could be acquired until after it had been approved by Congress or a competent tribunal appointed by Congress. Furthermore, since neither condition had been met when Mexico ceded California to the United States in 1848, any grant made before then was invalid and unenforceable against either party. As such, despite their claim of ownership based on an earlier grant from Mexico's government-in-exile during its war with Spain (1810–1821), their petition for a patent must fail as it did not meet all necessary requirements under U.S law at that time