I didn't know Hempel had a medical/licence restriction - the only person required to sight his medical would be his chief pilot. CASA should have notified his chief pilot. You can't blame anyone but CASA, chief pilot and Barry himself.
Yes, they should have in this case. Indeed the chief pilot should have known that Hempel had neither a CPL nor a Class 1 medical - both of which were required for the operations he was conducting. I have to show my licence and medical when I hire an aircraft.
But how can CASA notify everybody that a pilot may fly for, or hire an aircraft from? The coroner's recommendation that CASA publish a list of all restrictions on all medicals would have given CASA some deniability, but I doubt it would have stopped Hempel from flying.
Happy to continue this discussion on the more appropriate thread.