Penniman's Case is a United States Supreme Court case that dealt with the issue of whether a state court could issue a writ of habeas corpus to a prisoner who was being held in a federal prison. The case arose when a prisoner, William Penniman, was held in a federal prison in Massachusetts. Penniman sought a writ of habeas corpus from the state court, arguing that he was being held in violation of the Constitution. 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 power to issue such a writ. 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 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 Penniman's Case, 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 neither party resided within its boundaries and therefore it could not exercise personal jurisdiction over them. However, Justice Field dissented from this decision on the grounds that there were sufficient contacts between one of the parties and the forum state for it to be able to exercise personal jurisdiction over him. He argued that since one of the parties had been served with process while present in Pennsylvania, he should be bound by any judgment rendered against him in a suit brought there. Furthermore, Justice Field pointed out that if such service was insufficient for establishing personal jurisdiction then no foreign defendant would ever be subject to suit outside his own home state as long as he avoided being physically present within other states' borders when served with process. As such, Justice Field concluded that due process requirements were met and thus Pennsylvania courts had validly exercised their jurisdictional authority in this case