Prout v. Roby 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 a prisoner, Prout, was held in a federal prison in Massachusetts. Prout sought a writ of habeas corpus from the state court, claiming that he was being held in violation of the Constitution. The state court granted the writ, and the federal government appealed the decision to the Supreme Court. The Supreme Court held that the state 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 remedy, 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 remedy that could only be used to challenge the legality of a person's detention, and not to challenge the conditions of the detention. The Court's decision in Prout v. Roby established that state courts do not have the authority to issue writs of habeas corpus to prisoners held in federal prisons. This decision has been cited in numerous subsequent cases, and has been used to support the principle that state courts cannot interfere with the federal government's authority to imprison individuals.

Justice Field delivered the dissenting opinion in Prout v. Roby, arguing that the majority had misinterpreted a key provision of the Bankruptcy Act of 1867. He argued that Congress intended to allow debtors to discharge their debts without having to pay any interest on them, and thus he disagreed with the majority's decision requiring payment of post-petition interest as part of a debtor's obligation under Section 17a(2). Field further noted that if Congress had wanted such an interpretation it would have been explicitly stated in the statute itself or its legislative history. Finally, Justice Field concluded by asserting his belief that allowing debtors to discharge their debts without paying post-petition interest was consistent with public policy and should be upheld by this Court.