It will be interesting to see how all this plays out.
If CASA roll over on this it will set a precedence for other certificate holders to ignore CASA directions.
This behavior by NAC certainly isn't good for aviation safety in PNG as a whole. Hagen airport should also be immediately closed, the main runway it's an absolute disgrace particularly given that it's only just been upgraded and resurfaced - concrete to fill the pot holes and the corrugations! It reminds me of Ononge.
The revenue that NAC are getting doesn't appear to be going into safety and critical aerodrome maintenance.