United States v. Mullan was a United States Supreme Court case that dealt with the issue of whether a federal court had the authority to issue a writ of habeas corpus to a prisoner held in a state prison. The case involved a prisoner, John Mullan, who was convicted of murder in the state of Pennsylvania and sentenced to life in prison. Mullan sought a writ of habeas corpus from a federal court, claiming that his conviction was unconstitutional. The Supreme Court held that a federal court did not have the authority to issue a writ of habeas corpus to a prisoner held in a state prison. The Court reasoned that the writ of habeas corpus was a remedy available only to prisoners held in federal custody, and that the federal court did not have the authority to interfere with the state court's decision. The Court also noted that the writ of habeas corpus was not available to prisoners held in state custody, as the writ was intended to protect the rights of prisoners held in federal custody. The Court concluded that the federal court did not have the authority to issue a writ of habeas corpus to a prisoner held in a state prison.

Justice Field delivered the dissenting opinion in United States v. Mullan, arguing that the majority's decision was contrary to both precedent and sound policy. He argued that Congress had not intended for a tax on distilled spirits to be imposed on those who produced them before they were sold or removed from the distillery, as this would lead to double taxation of such products. Furthermore, he noted that if such a tax were allowed it could potentially be extended beyond just distilled spirits and applied to other goods as well; thus creating an undue burden on producers of these goods. Finally, Justice Field argued that allowing such taxes would also create an unfair advantage for large-scale manufacturers over smaller ones since larger companies are better able to absorb additional costs associated with taxation than their smaller counterparts.