An ASIC is just that - an identity card. It means you have undergone a standardised check of your background. That's all. It is just one part of the security control measures airports are required by law to implement to control access to various designated parts of the aerodrome. You also have to be an "authorised person" ie not one of these:
unauthorised person, in relation to a place or thing, means a person who:
(a) is not authorised by the owner or person in control of the place or thing to have access to the place or thing; and
(b) has no other lawful reason to have access to the place or thing.