The use of a military tribunal provoked criticism from former Attorney General Edward Bates and Secretary of the Navy Gideon Welles, who believed that a civil court should have presided, but Attorney General James Speed pointed to the military nature of the conspiracy and the facts that the defendants acted as enemy combatants and that martial law was in force at the time in the District of Columbia. (In 1866, in Ex parte Milligan, the United States Supreme Court banned the use of military tribunals in places where civil courts were operational.) Only a simple majority of the tribunal members was required for a guilty verdict, and a two-thirds for a death sentence. There was no route for appeal other than to President Johnson.