(1) A suspected international terrorist may appeal to the Special Immigration Appeals Commission against his certification under section 21.
(2) On an appeal the Commission must cancel the certificate if-
(a) it considers that there are no reasonable grounds for a belief or suspicion of the kind referred to in section 21(1)(a) or (b), or
(b) it considers that for some other reason the certificate should not have been issued.
(3) If the Commission determines not to cancel a certificate it must dismiss the appeal.
(4) Where a certificate is cancelled under subsection (2) it shall be treated as never having been issued.
(5) An appeal against certification may be commenced only-
(a) within the period of three months beginning with the date on which the certificate is issued, or
(b) with the leave of the Commission, after the end of that period but before the commencement of the first review under section 26.