Ex parte Milligan
A military court may not try an ordinary citizen unconnected with the military or an area of the country directly involved in war. The jurisdiction to try this citizen falls to the civil and federal courts. The right to a trial by jury is preserved, and regardless of whether the citizen is guilty of the crimes tried by the military court, the court may not pass judgment nor sentence the individual.
During the Civil War, Lambdin Milligan was charged by a military commission of conspiring against the federal government. Some of the charges included giving aid and comfort to the rebels and inciting an insurrection. He was also charged with disloyal practices and violations of the laws of war.
The military commission charged that he, with others, conspired to seize the U.S. state arsenal, and to release the prisoners of war confined in the military prison. Then, the commission charged, Milligan planned to arm these prisoners, and join the forces of the South who planned to invade the states of Kentucky, Indiana, and Illinois. Milligan was convicted and sentenced to hang. He appealed his case to the Supreme Court.
Justice Davis, delivering the opinion of the Court, said the U.S. circuit court had authority to certify questions in a proceeding for a writ of habeas corpus to inquire into a sentence of a military commission, and that the Supreme Court has jurisdiction to hear and determine them. The act of Congress "relating to habeas corpus" approved 3 March 1863, conferred jurisdiction on the circuit court of Indiana to hear such a case.
Davis said that a military commission had no jurisdiction to try and sentence someone who was not a resident of one of the rebellious states, nor a prisoner of war. Davis believed that Congress can grant no such power. The right of trial by jury is preserved to everyone accused of crime, who is not attached to the military in actual service.
Martial law, Justice Davis wrote, cannot arise from a threatened invasion. The invasion must be real, such as one that closes the courts and deposes the civil administration. Military rule can never exist where the courts are open, and in the proper and unobstructed exercise of their jurisdiction. Davis also wrote that the suspension of the privilege of the writ of habeas corpus does not suspend the writ itself. The writ issues as a matter of course; and on the return made to it the court decides whether the party applying is denied the right of proceeding any further with it.
If the military trial of Milligan was contrary to law, then he was entitled, on the facts stated in his petition, to be discharged from custody by the terms of the act of Congress of 3 March 1863. He could not be treated as a prisoner of war, when he had lived in Indiana for over 20 years and was arrested there.
Justice Chase delivered a concurring order but a different opinion. He was joined by Justices Wayne, Swayne, and Miller. He stated that though the crimes with which Milligan was charged were of the gravest character, it is more important to the country and to every citizen that he should not be punished under an illegal sentence, sanctioned by the Supreme Court, than that he should be punished at all. The laws which protect the liberties of the whole people must not be violated or set aside in order to inflict, even upon the guilty, unauthorized though merited justice.