169. (1) No president or member of a court martial, no judge advocate, no party to any proceedings before a court martial, or his legal practitioner or agent, and no witness acting in obedience to a summons or order to attend a court martial shall, while proceeding to, attending, or returning from, a court martial, be liable to arrest under civil or revenue process. (2) If any such person is arrested under any such process, he shall be discharged by order of the court martial.