12. Restriction on right of entry---(1) Notwithstanding anything in
 section 11 of this Act, the Commission or any employee of the Department
 of Labour may be refused entry to any premises or to any part of any
 premises on the grounds that the exercise in respect of those premises
 or that part of those premises of the right of entry conferred by that
 section might prejudice---
   (a) The security or defence of New Zealand; or
   (b) The investigation or detection of offences.

   (2) Where the Attorney-General certifies in respect of any premises or
 any part of any premises that the exercise of the right of entry
 conferred by section 11 of this Act in respect of any premises might
 prejudice---
   (a) The security or defence of New Zealand; or
   (b) The investigation or detection of offences,---

 that certificate shall be conclusive evidence that grounds exist under
 subsection (1) of this section for refusing entry to those premises or
 that part of those premises.