Sorry to bring up an old thread however its the only one I could find regarding laws around going de-cat. After being unable to find any definite answers I thought id find it myself, s43a of the EPA Act 1970 pertains to operating a vehicle on the roads without the equipment required by regulations to reduce emissions. The current fine is 60 penalty units, 1 penalty unit equates to $158.57 in Victoria, bringing the fine to $9,532.20.