Excuse for physical disability; penalty for absence.

No officer or soldier of the National Guard, when ordered on duty to aid the civil authorities, or when ordered into the service of the United States in obedience to the call or order of the President, shall be excused from such duty except upon the certificate of the surgeon of his command of physical disability, such certificate to be presented to the Commanding General in case of an officer, or to his company commander in case of a soldier. If such officer or soldier fail to furnish such excuse he shall be tried and punished by a court-martial. For absence from any other military duty required or ordered under the provisions of this chapter the penalty shall be such as may be prescribed by the Commanding General, or the bylaws of the organization to which the officer or soldier belongs.