Doolan v. Carr was a United States Supreme Court case that addressed 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, John Doolan, was held in a federal prison in the state of New York. Doolan sought a writ of habeas corpus from the state court, claiming that he was being held in violation of his constitutional rights. 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 authority to interfere with the federal government's power 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 prisoner's detention, and not to challenge the conditions of the prisoner's confinement. The Court's decision in Doolan v. Carr established that state courts do not have the authority to issue writs of habeas corpus to prisoners held in federal prisons. The decision also clarified the scope of the writ of habeas corpus, and established that it could only be used to challenge the legality of a prisoner's detention, and not to challenge the conditions of the prisoner's confinement.

In Doolan v. Carr, the Supreme Court was asked to decide whether a state law that allowed for the sale of property belonging to an insolvent debtor violated the Constitution's Contract Clause. The majority opinion held that it did not violate this clause and upheld the law in question. However, Justice Field dissented from this decision and argued that such a law interfered with contractual rights by allowing creditors to be paid out of assets which were intended for other purposes as specified in contracts between debtors and their creditors. He further stated that while states have broad powers over matters related to bankruptcy proceedings, they cannot use those powers so as to impair existing contract obligations or interfere with vested rights without violating constitutional principles established by Article I Section 10 of the United States Constitution.