Not sure about the new laws, but I know they only just changed. From the Office of Road Safety in WA. Would seem strange to change again so quickly although not out of the ordinary for WA.
http://www.ors.wa.gov.au/_layouts/getAsset.aspx?URI=2916932&REV=1&RCN=D10#224179Carriage of additional passengers, where
there are no seat belts or child restraints
New laws came into effect on 1 October 2010 that introduced new rules for the restraint of
children and adults. These amendments follow those made at the national level under the
Australian Road Rules.
While there were rules prohibiting the carriage of unrestrained passengers in the backs of utes,
trucks and panel vans in WA since 2006, there were no restrictions in the case of more passengers
in the main body of the vehicle than available seat belted positions.
This situation was of grave concern given the importance of restraints in protecting occupants from
injury in the event of a collision.
To address this concern a key new rule for drivers and passengers of motor vehicles has therefore
been introduced.
Only passengers that are sitting in a seat fitted with a seat belt (or child restraint) with the seat belt
(or restraint) fastened and worn correctly can be carried in the vehicle.
No additional unrestrained passengers, including in the rear of station wagons, is permitted.
Passengers must not occupy the same seating position as another passenger.
The rule does not apply to motorcycles or other vehicles without seat belts fitted.
There is no requirement for older vehicles that are not fitted with seat belts to have them fitted.
If a vehicle does not have a seat belt or approved child restraint fitted to all its passenger seats, and
a passenger has a legal exemption from wearing a seat belt under the code (i.e. medical certificate),
then in this case those seats fitted with a restraint should be used first by those legally required to
wear a restraint
