(1)In proceedings for an offence under section 2 it is a defence for the accused to prove that his conduct was prevented from being a contravention of that section by the provisions of this section.
(2)It is not a contravention of section 2 for a person to participate in the transfer of a prohibited object if—
(a)he does so with the intention that it will be used only for purposes permitted by subsection (7); and
(b)the transfer in question is authorised by the Secretary of State for the purposes of this subsection.
(3)It is not a contravention of section 2 for a person—
(a)to participate in the transfer of a prohibited object for the purpose only of enabling it to be destroyed; or
(b)to have such an object in his possession for the purpose only (with or without such a transfer) of securing its destruction.
(4)It is not a contravention of section 2 for a person to have a prohibited object in his possession if—
(a)he has it in his possession with the intention that it will be used only for purposes permitted by subsection (7); and
(b)it is an object which the Secretary of State has authorised him for the purposes of this subsection to have in his possession.
(5)It is not a contravention of section 2 for a person to participate in the acquisition of a prohibited object if—
(a)the acquisition that has been made, agreed or arranged is an acquisition by means of a transfer which is permitted by virtue of subsection (2) or (3); and
(b)he participates in that acquisition—
(i)with the intention that the object will be used only for purposes permitted by subsection (7); or
(ii)for the purpose (with or without a further transfer) of enabling the object to be destroyed.
(6)It is not a contravention of section 2 for a person at any time to assist, encourage or induce any conduct if, at that time, he has reasonable cause to believe—
(a)that the conduct in question is conduct which is or will be prevented by the provisions of this section from being a contravention of section 2; or
(b)that it would be so prevented if it were not otherwise prevented from being such a contravention.
(7)The purposes permitted by this subsection are—
(a)the development of techniques of mine detection, mine clearance or mine destruction;
(b)training in techniques of mine detection, mine clearance or mine destruction; and
(c)the purposes of any proceedings under this Act or of any criminal investigation or other criminal proceedings in which the object in question is or may be evidence.
(8)No person shall be authorised by the Secretary of State for the purposes of subsection (2) or (4) to transfer, or to have in his possession, any prohibited objects of any description in numbers in excess of what is necessary for the purposes permitted by subsection (7).