The authority of the Secretary of State is not required by virtue of subsection (1)(aba), (b) or (c) of section 5 of the 1968 Act for a person to have in his possession, or to purchase or acquire, or to sell or transfer, any firearm, weapon or ammunition designed or adapted for the purpose of tranquillising or otherwise treating any animal, if he is authorised by a firearm certificate to possess, or to purchase or acquire, the firearm, weapon or ammunition subject to a condition restricting its use to use in connection with the treatment of animals.