France v. State of Missouri was a case heard by the United States Supreme Court in 1895. The case involved a dispute between the State of Missouri and the French government over the ownership of certain lands in the state. The French government had acquired the lands in question in 1803, but the State of Missouri had since passed a law claiming ownership of the lands. The French government argued that the law was unconstitutional, as it violated the Treaty of 1803, which had granted the lands to France. The Supreme Court ultimately sided with the French government, ruling that the law passed by the State of Missouri was unconstitutional. The Court held that the Treaty of 1803 was a valid agreement between the United States and France, and that the State of Missouri could not pass a law that violated the terms of the treaty. The Court also held that the French government had a valid claim to the lands in question, and that the State of Missouri could not take them without the consent of the French government. As a result, the Court ruled in favor of the French government and ordered the State of Missouri to return the lands to France.

Justice Harlan delivered the dissenting opinion in France v. State of Missouri, arguing that the state's tax on foreign-owned property was unconstitutional and violated the treaty between France and America. He argued that a state cannot impose taxes on foreign-owned property without violating international law, which is binding upon all states under Article VI of the Constitution. Furthermore, he noted that treaties are part of federal law and should be respected by all states as such; thus, any attempt to levy a tax on foreign-owned property would be an infringement upon this federal power. Finally, Justice Harlan asserted that if individual states were allowed to impose their own taxes on foreign-owned property it could lead to conflict with other nations or even war due to conflicting laws among different jurisdictions within one nation. Therefore, he concluded that allowing such taxation would undermine both national sovereignty and international peace.