16 The respondent's first submission appears to be founded on the proposition that there was nothing erroneous or irregular in the magistrate's order imposing the special penalties. On the materials before him, no challenge having been made to the validity of the regulations, his order was correct. In the absence of challenge he was entitled to presume that the regulations were valid. Aliter if they were challenged (see Brudenell v Nestle Co (Aus) Ltd [1971] VicRp 27; [1971] VR 225 at 233). In my opinion, this foundation is sound. The order was a valid order which would provide a firm authority for the collection of the fines. But it was not thereby rendered immune. It was still subject to whatever challenges the law could provide. It could be set aside on appeal on the ground that the regulations were ultra vires and void. In some cases of this kind, and perhaps in this case, other avenues of correction, such as the prerogative writs, would be available. It is true that, if no avenue for correction of the magistrate's order was available, the collection of the fines could not be successfully opposed because the law would not permit anyone to go behind the order of the court. But the fact that in such a proceeding the question of the validity of the regulations could not be debated does not give the regulation itself any validity. Further, the absence of challenge at trial to the validity of the regulation, while entitling the magistrate to make his order, had no effect on the regulation itself, and of course the validity of the regulation was challenged by the application of the 15 October 1986. The question for his Worship then was not whether the regulation should be presumed to be valid, but whether it was. In my view he rightly decided that it was not. If it was invalid when made it remained invalid and it would follow that penalties imposed in reliance upon it were unauthorised and "contrary to the law". It is that fact which invoked the magistrate's jurisdiction to amend the order and that would remain a fact even if all avenues of correction by ordinary appellate processes were closed.