21Exclusion from registers of information affecting national security
(1)No information shall be included in a register maintained under section 20 above if and so long as, in the opinion of the Secretary of State, the inclusion in the register of that information, or information of that description, would be contrary to the interests of national security.
(2)The Secretary of State may, for the purpose of securing the exclusion from registers of information to which subsection (1) above applies, give to enforcing authorities directions—
(a)specifying information, or descriptions of information, to be excluded from their registers; or
(b)specifying descriptions of information to be referred to the Secretary of State for his determination;
and no information referred to the Secretary of State in pursuance of paragraph (b) above shall be included in any such register until the Secretary of State determines that it should be so included.
(3)The enforcing authority shall notify the Secretary of State of any information it excludes from the register in pursuance of directions under subsection (2) above.
(4)A person may, as respects any information which appears to him to be information to which subsection (1) above may apply, give a notice to the Secretary of State specifying the information and indicating its apparent nature; and, if he does so—
(a)he shall notify the enforcing authority that he has done so; and
(b)no information so notified to the Secretary of State shall be included in any such register until the Secretary of State has determined that it should be so included.