Woolf v. Hamilton et al. 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 held in federal custody. The case arose when a prisoner, Woolf, was held in federal custody in the District of Columbia. Woolf sought a writ of habeas corpus from the state court of the District of Columbia, which the court granted. The federal government then 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 federal custody. The Court reasoned that the power to issue writs of habeas corpus was a power reserved to the federal government, and that the state court did not have the authority to interfere with the federal government's power. The Court also noted that the state court's decision was in conflict with the Constitution, which gave the federal government exclusive jurisdiction over matters involving federal prisoners. The Court's decision in Woolf v. Hamilton et al. established that state courts do not have the authority to issue writs of habeas corpus to prisoners held in federal custody. This decision has been cited in numerous subsequent cases involving the power of state courts to issue writs of habeas corpus.

In Woolf v. Hamilton et al., the Supreme Court was asked to decide whether a state court had jurisdiction over an action brought by a citizen of one state against citizens of another. The majority opinion held that it did not, as the Constitution does not grant such authority to states and Congress has never passed legislation granting them this power. Justice Field dissented from this decision, arguing that while he agreed with the majority's conclusion on constitutional grounds, there were other considerations at play in determining whether or not a state court could exercise jurisdiction over such matters. He argued that if Congress had granted states this power through legislation then they should be allowed to do so; however, since no such law existed at the time of his dissent he concluded that it would be inappropriate for him to support any ruling which would give states more authority than what is explicitly provided for in either federal or state laws.