I do not have knowledge of the CASA situation. But in other areas of federal government inspectors / representatives you don't need to allow access with no notice or necessarily at the timeframe nominated by the official. It is acceptable to offer to co-operate fully but because of xxxxx (insert appropriate reason), now is not suitable and an appointment is made for another time. The strategy is to buy enough time to collect your thoughts & arrange a lawyer to be present. There is no question about not co-operating. You will co-operate fully when you have the opportunity to re-arrange your affairs. Its a matter of arranging a time to properly do the inspection / interview. It could be argued that a demand that you drop everything to comply at the inspectors timeframe is bullying.