Thank you for the question.
Section 54 of the act contains the requirements for applications for firearms licences and registration certificates, as well as that for applying for authorizations to carry and authorizations to transport. Authorizations to carry can be made for reasons of either employment or protection of life. Most of the ATCs that are given in Canada are for reasons of employment—as you've noted, for security guards—or in terms of personal protection when they are employed.
Clause 27 amends paragraph 54(2)(a) to specify that applications for a licence or an ATC for lawful profession or occupation purposes must be made to a CFO, except in the cases under paragraph 20(a) in terms of protection of personal life. In those cases, it would be changed from the CFO to the commissioner of firearms.