Section 4 has the effect that (leaving aside taxation laws), "[t]he provisions of the laws of a State as in force at a time (whether before or after the commencement of this Act) apply, or shall be deemed to have applied, in accordance with their tenor, at that time in and in relation to each place in that State that is or was a Commonwealth place at that time" (s 4(1)) - unless the State law already had that application, in which case the State law applied untouched (s 4(3)).
There is also express provision in s 5 concerning the operation of some Commonwealth crimes provisions.
But as a general matter, if smoking is illegal just outside the Commonwealth place, it will be illegal inside it.
eta: oops, I left this open for a while before posting, and just saw others have answered.
I had friends who smoked a joint outside Kiribilli House when they were young and stupid. AFP came out, looked at them, shook their heads and walked off
It's in my comment history here already, and is public information.
It's a mildly interesting story too, because it proves, at least back then, that South Australian police can't always run roughshod over your rights to privacy.
They had to drop the charges due to acting illegally, and I got all my cash back. Ha!
Australia has federal legislation that applies state law to federal land, in general (the Commonwealth Places (Application of Laws) Act 1970).
(Also, it's only major airports - state capital city airports, plus a handful of regional airports that were formerly owned by the Federal Airports Corporation - that are federal land. Most airports in Australia are small regional airports that are and were always owned by local government and not subject to the special federal land ownership and leasing regime of the major airports.)
It is operated by a private company, but as a former Federal Airports Corporation airport, the land on which the airport is built is owned by the Commonwealth and leased to the private operator on a 99-year lease.
The joint didn't magically teleport into the square of federal property, so possession before you stepped onto the federal land seems like a fairly easy argument. But I suspect the cops have a lot better things to do.
Allow me to introduce the Commonwealth Places (Application of Laws) Act 1970 to you. [https://www.legislation.gov.au/Details/C2016C00956]
Section 4 has the effect that (leaving aside taxation laws), "[t]he provisions of the laws of a State as in force at a time (whether before or after the commencement of this Act) apply, or shall be deemed to have applied, in accordance with their tenor, at that time in and in relation to each place in that State that is or was a Commonwealth place at that time" (s 4(1)) - unless the State law already had that application, in which case the State law applied untouched (s 4(3)).
There is also express provision in s 5 concerning the operation of some Commonwealth crimes provisions.
But as a general matter, if smoking is illegal just outside the Commonwealth place, it will be illegal inside it.
eta: oops, I left this open for a while before posting, and just saw others have answered.