Whoa there fellas! This is getting just a little bit complicated.
The Civil Aviation Act and the Air Navigation Act and the CARs, CAOs, CASRs, ANRs etc are all pieces of Commonwealth legislation. But don't confuse any of those pieces of legislation for positive authority to trespass on anyone's property or to cause them a nuisance. For example, reg 93 of the CARs says:
Protection of certain rights
Nothing in these regulations shall be construed as conferring on any aircraft, as against the owner of any land or any person interested therein, the right to alight on that land, or as prejudicing the rights or remedies of any person in respect of any injury to persons or property caused by the aircraft.
Owners of land can take actions in trespass for infringements of airspace above their land. Typical examples are branches of trees that infringe only the airspace above the adjacent land; roofs or awnings of buildings that infringe only the airspace on adjacent land. A jib of a crane that would swing over an adjacent property in high winds has been found to be trespassing that adjacent property. A bullet fired into a property has been found to be a trespass of that property, even though it only traversed airspace above the property (before lodging, tragically and fatally, in a noisy cat).
The important questions are: at what height above a property does a thing have to be before it will cease to be trespassing that property, and what factors, if any, (such as the state of mind of the property owner and the motivation of the alleged trespasser) will affect that height so far as aircraft are concerned? Lord Bernstein's case suggests at least that an aircraft in the normal course of navigation and in compliance with the air rules will not be trespassing, as a matter of common law.
In NSW and jurisdictions that have the equivalent of subsection 2(1) of the NSW Damage by Aircraft Act, the answer does not matter, provided the aircraft is at a height above the ground, which, having regard to wind, weather, and all the circumstances of the case is reasonable, or the ordinary incidents of such flight, and the provisions of the Air Navigation Regulations are duly complied with.
If you are at YSBK for example, taking off or landing, or practising missed approaches, you are probably protected from actions in trespass and nuisance (provided you are not doing circuits at 50').
If you start practising a forced landing (anywhere in Australia) into someone's property, things start to get a bit risky if you go below 500' or, if it's a populous area, below 1000'.
Building an airstrip does not constitute an open invitation to any aircraft to pop in or shoot a missed approach there. I can't see any reason in principle that prohibits the owner of land from saying, in effect, that she will consent to something which might otherwise be a trespass and nuisance (e.g. doing a touch and go on, or shooting a missed approach into, her airstrip), on payment of a fee.