The U.S. Supreme Court case Perez Y Fernandez v. Fernandez Y Perez in 1910 revolved around a dispute over the inheritance of property located in Puerto Rico, which was acquired during Spanish sovereignty but had not been registered according to Spanish law at the time of acquisition. The plaintiffs argued that they were entitled to inherit as per American laws since Puerto Rico became an American territory before the death of their relative who owned the property. However, defendants claimed that under Spanish law, unregistered properties could not be inherited and thus it should belong to them as they occupied and cultivated it for many years after its owner's death. The court ruled against the plaintiffs stating that although Puerto Rico is now part of America, this does not change or affect rights acquired under former sovereigns such as Spain unless expressly stated by Congress. Therefore, even though current American laws allow inheritance regardless if a property is registered or not; these cannot apply retroactively on properties obtained during previous sovereignties with different rules regarding registration and ownership transfer.

The dissenting opinion in the Perez Y Fernandez v. Fernandez Y Perez case argued that the majority's decision to uphold a lower court ruling, which denied an inheritance claim on the grounds of illegitimacy, was flawed. The dissenting justices believed that this interpretation of Spanish law - under which Puerto Rico operated at the time - was incorrect and unfairly penalized children born out of wedlock. They contended that Spanish law did not categorically deny inheritance rights to illegitimate children but instead allowed for such claims if certain conditions were met, including recognition by the father or a legal judgment establishing paternity. Therefore, they felt it unjust to disallow these individuals from claiming their rightful inheritances based solely on their birth circumstances.