No trial or other proceeding held or taken before, and no sentence passed by a court-martial or any other authority under any military, naval and air force law before the 30th day of June, 1966, shall be called in question in any court merely on the ground that the court-martial or other authority had no jurisdiction by virtue of the provisions of the principal Act, and all such trials, proceedings and sentences shall, notwithstanding any judgment or order of any court, be as valid and operative as if they had been held, taken or passed in accordance with law; and accordingly no suit or other legal proceeding shall be maintained or continued against any person whatever on the ground that any such trial, proceeding or sentence was not held, taken or passed in accordance with law.