(a) Summary courts-martial may be convened by--

(1) any person who may convene a general or special court-martial;

(2) the commanding officer of a detached or separate company or corresponding unit or other detachment of a force of the organized militia;

(3) the commanding officer or officer in charge of any other command when empowered by the adjutant general.

(b) When but one officer is present with a command or detachment he shall be the summary court-martial of that command or detachment and shall hear and determine all summary court-martial cases brought before him. Summary courts-martial may, however, be convened in any case by superior competent authority when deemed desirable by him.