(1) Nothing in section 47 applies-
(a) to an act which is authorised under subsection (2); or
(b) to an act done in the course of an armed conflict.
(2) The Secretary of State may-
(a) authorise any act which would otherwise contravene section 47 in such manner and on such terms as he thinks fit; and
(b) withdraw or vary any authorisation given under this subsection.
(3) Any question arising in proceedings for an offence under section 47 as to whether anything was done in the course of an armed conflict shall be determined by the Secretary of State.
(4) A certificate purporting to set out any such determination and to be signed by the Secretary of State shall be received in evidence in any such proceedings and shall be presumed to be so signed unless the contrary is shown.