Horn v. Lockhart et al. was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner who was being held in a federal prison. The case arose when the petitioner, Horn, was convicted of a crime in Arkansas and sentenced to a term of imprisonment in the federal penitentiary in Little Rock. Horn then filed a petition for a writ of habeas corpus in the Arkansas Supreme Court, arguing that his conviction was unconstitutional. The Arkansas Supreme Court granted the writ and ordered Horn to be released from federal custody. The United States Supreme Court, however, held that the Arkansas Supreme Court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. The Court reasoned that the writ of habeas corpus was a federal prerogative and that the state court did not have the power to interfere with the federal government's authority to imprison individuals. The Court also noted that the writ of habeas corpus was a fundamental right that could not be taken away by the states. Ultimately, the Court held that the Arkansas Supreme Court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. The Court reasoned that the writ of habeas corpus was a federal prerogative and that the state court did not have the power to interfere with the federal government's authority to imprison individuals. The Court also noted that the writ of habeas corpus was a fundamental right that could not be taken away by the states.

Justice Field delivered the dissenting opinion in Horn v. Lockhart et al., arguing that the majority's decision was incorrect and should be reversed. He argued that under Arkansas law, a judgment creditor had no right to levy on property owned by an insolvent debtor unless it was done through legal process, such as garnishment or attachment. In this case, however, there had been no legal process used; instead, the creditors simply seized possession of the property without any court order or other authority from a court of law. Justice Field further noted that even if there had been some form of judicial action taken against Horn prior to his death - which he believed unlikely - it would not have given them title to his estate since they were not parties in interest at the time of his death and thus could not claim any rights over it after he passed away. As such, Justice Field concluded that Lockhart et al.'s seizure of Horn's estate was unlawful and should be reversed by reversing the lower court's ruling in favor of them.