Section 15

Nothing in this Part shall extinguish or abridge any powers or authorities which, if this Act had not been passed, would have been exercisable by virtue of the prerogative of the President or the Government, or any powers or authorities conferred on the President or the Government by any written law, and, in particular, nothing in this Part shall extinguish or abridge any such powers or authorities, whether in time of peace or of war, for the purpose of the defence of the nation or of training, or maintaining the efficiency of, the armed forces.

Where in any proceedings under this Act it is material to determine whether anything was properly done or omitted to be done in the exercise of the prerogative of the President or the Government, the President may, if satisfied that the act or omission was necessary for any such purpose as is mentioned in subsection (1), issue a certificate to the effect that the act or omission was necessary for that purpose; and the certificate shall, in those proceedings, be conclusive as to the matter so certified.