Hey Doug. There is a national regulator for refrigerant handling. So need a national licence to handle refrigerant (including mount and piping the units) And then some states have a local regulator and licence (qld has one but SA does not)
It is more about them cashing in than stopping people releasing gases into ozone. But technically yes it illegal and against at least a federal law about ozone emissions. Funny how you can open a mechanical workshop and work on cars etc without qualifications but can't put up an air con on your own property. But your work is still fantastic mate and the air con works great in the games room!
Check out these installs: