Hanauer v. Woodruff 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 held in a federal prison. The case arose when a prisoner, Hanauer, was held in a federal prison in the state of Georgia. Hanauer sought a writ of habeas corpus from the state court, which was denied by the federal 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 authority to interfere with the federal government's power to imprison individuals. The Court also noted that the writ of habeas corpus was a fundamental right and that the state court should not be allowed to interfere with the federal government's power to imprison individuals. The Court concluded that the state court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison.

In Hanauer v. Woodruff, the Supreme Court was tasked with deciding whether a state court had jurisdiction to hear a case involving an alleged breach of contract between two parties from different states. The majority opinion held that the state court did have jurisdiction and affirmed the judgment of the lower courts. However, Justice Field dissented on this ruling, arguing that it violated Article III of the Constitution which grants exclusive federal judicial power over cases involving citizens from different states or foreign countries. He argued that since both parties in this case were citizens of different states, only a federal court could properly adjudicate their dispute and thus any decision by a state court would be unconstitutional and voidable under existing law.