We operate on exceptions to certain regulations, under strict conditions. Should the regulator believe we aren't adhering to these conditions or that it's no longer in the public's safety they can withdraw them at any time. A good example would be the Jabiru Engine, a few bad types of engines but it was easier to enforce on the whole lot.
I'm not supporting the case for it to happen so can't really give you a reason for it, but if CASA were to believe there was a major issue within RA-AUS (training, pilot airmanship, maintenance) you can bet they will act swiftly and ask questions later. (I'm not suggesting there is any such issue).