The Act does not require CASA to ensure the existence of a civil aviation sector at all. merely to ensure "safety."
thus it is possible for CASA to discharge any and all of its responsibilities under the Act by preventing flying at all.
it follows that the only errors CASA can commit and be held to account for are by permitting aviation to occur.
Therefore CASA Is never in challengeable error if it prevents aviation from occurring.
the rest is history - everything is prohibited except by reference to exemptions.