In the Virginia National Guard military judges whenever they sit on a military court, and otherwise presidents of courts-martial and summary court officers, shall have power to issue warrants to arrest accused persons and to bring them before the court for trial whenever such persons shall have disobeyed an order in writing from the convening authority to appear before such court, a copy of the charge or charges having been delivered to the accused with such order, and to issue commitments in carrying out sentences of confinement, and to issue subpoenas and subpoenas duces tecum, and to enforce by attachment attendance of witnesses and the production of books and papers, and to sentence for a refusal to be sworn or to answer as provided in actions before civil courts. They shall also have power to punish for contempt occurring in the presence of the court.