Nothing in Parts II to IV shall render unlawful an act done for the purpose of safeguarding national security.
A certificate purporting to be signed by or on behalf of a Minister of the Crown and certifying that an act specified in the certificate was done for the purpose of safeguarding national security shall be conclusive evidence that it was done for that purpose.
A document purporting to be a certificate such as is mentioned in subsection (2) shall be received in evidence and, unless the contrary is proved, shall be deemed to be such a certificate.