On these charges and specifications, Milligan was subjected to a lengthy trial by this Military Commission which finally found him guilty on all the charges and sentenced him to be hanged. The record was approved by the Commanding General, and then transmitted to President Lincoln, who held it long under advisement, and was so holding it when he was killed. His successor, at about the same time that he summoned the Commission to try Mrs. Surratt, at length approved the findings and ordered the sentence to be executed on Friday, the 19th day of May, 1865.
But this object-lesson to the Commission sitting at that date in the old Penitentiary was intercepted. On the 10th of May, Milligan brought the record before the United States Circuit Court by a petition for his discharge, and, the two judges differing upon the main question of the jurisdiction of the Commission, the cause was certified under the statute to the Supreme Court of the United States; in deference to which action the President suspended the execution. The argument before that high tribunal coming on in the winter of 1865-66, a great array of counsel appeared upon both sides; David D. Field, James A. Garfield and Jeremiah S. Black for the prisoner, and Attorney-General Speed and Benjamin F. Butler for the United States. The counsel for the Government followed the same line as did Judge Bingham in his argument on the "Conspiracy Trial;" the counsel for the prisoner on their side, only enlarging, emphasizing and enforcing the argument of Reverdy Johnson. At the close of the term the Court unanimously decided that the Military Commission had no jurisdiction to try Milligan; that its verdict and sentence were void; and ordered the defendant discharged.
At the next term, the Court handed down two opinions--one the opinion of the Court, read by Judge Davis, in which four of his colleagues concurred, and one by Chief-Justice Chase, in which three of his colleagues concurred. The two opinions agreed that, as matter of law, the President could not of his own motion authorize such a Commission, and that, as matter of fact, the Congress had not authorized such a Commission; and therefore they were at one in their conclusion. But they differed in this; that, whereas the majority of the Court held that not even the Congress could authorize such a Court, the minority, while agreeing that the Congress had not exercised such a power, were of opinion that such a power was lodged in that branch of the Government.