The U.S. Supreme Court case Diaz, in his own right, etc., et al. v. Carlota and Clementina Gonzalez y Lugo, etc., et al., 1922 revolved around the issue of property rights and inheritance laws under Spanish Civil Law as applied to Puerto Rico. The plaintiffs were heirs of a deceased woman who had left her estate to her two daughters (the defendants). The plaintiffs claimed that they should have been included in the distribution of the estate based on their relationship with the deceased through marriage or bloodline according to Spanish law which was still applicable at that time in Puerto Rico due to its status as an unincorporated territory of United States acquired from Spain after Spanish-American War. However, upon review by lower courts it was determined that these claims were not valid because they did not meet certain requirements set forth by said law such as being within a certain degree of kinship or having lived with the decedent for a specific period prior death. Upon appeal before Supreme Court it upheld this decision stating that while indeed some aspects of Spanish civil law remained effective post-acquisition unless specifically repealed by Congress; however those pertaining inheritance rights had already been superseded by American common-law principles thus rendering plaintiff's claim invalid.

The dissenting opinion in the case of Diaz v. Gonzalez y Lugo argued that the majority's decision was inconsistent with previous rulings and failed to properly consider Puerto Rican law. The dissent contended that under Puerto Rican law, a child born out of wedlock could only inherit from their biological father if they had been legally recognized by him during his lifetime. In this case, no such recognition had occurred; therefore, according to the dissenters, it was incorrect for the court to allow inheritance rights based on paternity established after death through DNA evidence or other means. They also expressed concern about potential negative impacts on estate planning and distribution due to uncertainty around posthumous paternity claims.