There's a summary offence in the NSW legislature from the "Motor Traffic Regulations" Body of Law (of 1935) which states that it is an offence to:
Open door of vehicle so as to cause danger to self/to other/to impede traffic.
It was repealed in 1999. Presumably one of the benefits of spending a little extra cash on a Special was that you had the luxury of legally unlocking and entering the vehicle via the driver's door in the comfort of your own driveway or garage
The fact that the law was repealed doesn't mean that it's now legal to endanger traffic in this way (of course). That offence is now covered by the "Australian Road Rules under the Road Transport (Safety and Traffic Management) (Road Rules) Regulation 1999":
A person must not cause a hazard to any person or vehicle by opening a door of a vehicle, leaving a door of a vehicle open, or getting off, or out of, a vehicle
What a mouthful
cheers
RET