Sections 57 of the Weapons Act Queensland states:
In this section-
weapon includes-
(a) an antique firearm, spear gun, long bow or sword; and
(b) a replica of a weapon; and
(c) a replica of a thing mentioned in paragraph (a); and
(d) a slingshot or shanghai
A person must not, without reasonable, carry a weapon exposed to public view in a public place
A person must not, without reasonable excuse, carry in a public place a loaded firearm or a weapon capable of being discharged.
A person must not, without reasonable excuse, discharge a weapon in, into, towards, over or through a public place
What would be a reasonable excuse?

Self defence was the only thing I could come up with but that's not allowed here anyway so left me wondering. Ideas?