In the case of Patstone v. Commonwealth of Pennsylvania, 1913, the U.S Supreme Court upheld a Pennsylvania law that prohibited non-citizens from owning firearms. The plaintiff, an Italian immigrant named John Patstone who had been living in the United States for over twenty years but never naturalized as a citizen, was convicted under this law after he shot and killed another man while hunting. He appealed his conviction to the Supreme Court on grounds that it violated his Fourteenth Amendment rights to equal protection under the law. However, Justice Oliver Wendell Holmes Jr., writing for a unanimous court, rejected this argument stating that states have broad powers to regulate gun ownership in order to protect public safety and welfare. Therefore they could legally discriminate between citizens and non-citizens in such regulations without violating their constitutional rights.

In the dissenting opinion for Patstone v. Commonwealth of Pennsylvania, Justice Holmes argued that the statute in question was unconstitutional because it violated equal protection rights under the Fourteenth Amendment. He contended that there was no rational basis for distinguishing between naturalized citizens and native-born citizens when it came to gun ownership rights. The law's prohibition on foreign-born individuals owning firearms, he believed, unfairly targeted a specific group without sufficient justification. Furthermore, he pointed out inconsistencies in how this law would be applied - an individual could legally own a firearm before becoming naturalized but would then become criminal upon taking their oath of citizenship if they continued to possess that same weapon. This inconsistency further highlighted what Holmes saw as arbitrary discrimination against immigrants by this legislation.