Ex parte Hughes 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 federal custody. The petitioner, John Hughes, was a prisoner in the custody of the United States Marshal for the District of Columbia. He had been convicted of a crime in the District of Columbia and was serving a sentence in the federal penitentiary. Hughes sought a writ of habeas corpus from the Supreme Court of the District of Columbia, claiming that his conviction was unconstitutional. The Supreme Court of the District of Columbia granted the writ, and the United States Marshal brought Hughes before the court. The United States Attorney for the District of Columbia argued that the state court did not have the authority to issue the writ, as the prisoner was in federal custody. The Supreme Court of the District of Columbia disagreed, ruling that the state court had the authority to issue the writ. The United States appealed the decision to the United States Supreme Court. The Supreme Court held that the state court did not have the authority to issue the writ, as the prisoner was in federal custody. The Court reasoned that the writ of habeas corpus was a federal remedy, and that the state court did not have the authority to issue the writ in a case involving a prisoner in federal custody. The Court also noted that the writ of habeas corpus was a federal remedy, and that the state court did not have the authority to issue the writ in a case involving a prisoner in federal custody.

In Ex Parte Hughes, the Supreme Court was asked to decide whether a state court had jurisdiction over an action brought by a non-resident against another non-resident. The majority opinion held that the state court did not have jurisdiction in this case because it lacked personal service of process on the defendant and therefore could not exercise its power over him. Justice Field dissented from this decision, arguing that states should be allowed to exercise their powers as long as they do so within constitutional limits. He argued that since there was no dispute about the facts or law involved in this case, it would be wrong for federal courts to interfere with how states choose to handle such matters. Furthermore, he noted that allowing states more control over these types of cases would help ensure uniformity among different jurisdictions and prevent forum shopping by litigants seeking favorable outcomes based on where they file suit.