The authority of the Secretary of State is not required by virtue of subsection (1)(aba) 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, a firearm if he is authorised by a firearm certificate to have the firearm in his possession, or to purchase or acquire it, subject to a condition that it is only for use in connection with the humane killing of animals.