Stone v. South Carolina was a United States Supreme Court case that addressed the issue of whether a state could impose a tax on a federal instrumentality. The case involved a dispute between the state of South Carolina and the United States government over a tax imposed by the state on the United States Post Office. The state argued that the tax was necessary to fund its public schools, while the federal government argued that the tax was unconstitutional because it interfered with the federal government's exclusive power to regulate interstate commerce. The Supreme Court ultimately sided with the federal government, ruling that the state of South Carolina could not impose a tax on a federal instrumentality. The Court reasoned that the federal government had exclusive power to regulate interstate commerce, and that the state's tax interfered with this power. The Court also noted that the tax was not necessary to fund the state's public schools, as the state had other sources of revenue available. As such, the Court held that the tax was unconstitutional and could not be imposed.

Justice Field delivered the dissenting opinion in Stone v. South Carolina, arguing that the majority had misapplied the law and failed to consider certain facts of the case. He argued that there was no evidence presented at trial to show that Stone's actions were done with malice or ill will, which is a necessary element for conviction under South Carolina's criminal libel statute. Furthermore, he noted that even if such evidence existed it would have been insufficient because truth is an absolute defense against criminal libel charges and Stone had testified at trial as to his belief in what he said about another individual being involved in a crime. Justice Field concluded by noting that while freedom of speech should not be abused, it must also be protected from unjustified government interference when used responsibly.