Fitzpatrick v. Flannagan 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, Fitzpatrick, was convicted of a crime in the state of New York and sentenced to a term of imprisonment in a federal prison. After serving his sentence, Fitzpatrick sought a writ of habeas corpus from the state court, arguing that he had been unlawfully detained in the federal prison. 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 prerogative, and that the state court did not have the power to interfere with the federal government's authority to detain prisoners. The Court also noted that the writ of habeas corpus was a remedy for unlawful detention, and that the state court had no jurisdiction to determine whether Fitzpatrick's detention was lawful or not. As a result, the Court held that the state court did not have the authority to issue the writ of habeas corpus.

Justice Field delivered the dissenting opinion in Fitzpatrick v. Flannagan, arguing that the majority had misapplied an earlier Supreme Court decision and failed to consider a state statute when ruling on the case. He argued that under Missouri law, which was applicable in this case, a contract for personal services could not be enforced against an executor or administrator of an estate unless it was approved by court order. The majority had relied upon a prior Supreme Court decision involving contracts between two private parties rather than one between a party and an executor or administrator of an estate as existed here. Justice Field further asserted that even if there were no such state law requirement, he would still dissent because he believed it would be unjust to allow someone who contracted with another person's representative without obtaining court approval to collect from their estate after they passed away.