I have had a good look through the Firearms Act. There is nothing ti say you prohibited from using a shotgun or rifle whilst ****ed or stoned.
However the chief officer of police has the powers to determine whether or not an individual is fit to possess and use firearms or shotguns. And this power can be exercised both at the time when a certificate is issued and whilst you in possession.
So if Chief officer of police is advised that a certain individual who holds a certificate was ****ed out of his head, was drunk and disorderly and somewhat rude to one of his officers, this would be taken into account. If it was then added that the individual was in the back of the pickup sitting next to a number of guns and cartridge bags with his mates and whilst the driver was not over the limit, all the other passengers were pretty intoxicated and swigging out of hip flasks, and that the reason the truck was pulled over was that he was mooning the pub out of the window as they left, it doesn’t paint a very good picture, especially when our ****ed individual the offers to show the female police sergeant his weaponry.
Compared to a police officer pulling a truck over. Driver completely sober, yes passengers had had a few drinks with the after shoot dinner but not intoxicated. Driver, who has a shotgun certificate, informed the police officer that the shotguns were all in the boot safe and secure, and and under three day rule he would ensure they were safely secured when they get to their destination etc.
It is all down to perception and behaviour. These days Police are under a lot of pressure and if there is any doubt as regards behaviour, the guns are removed from the equation immediately and then situation is sorted.
With a shotgun certificate there is three day borrowing rule whereby if you have a certificate you can take possession of shotgun for three days without having to do a formal transfer. I think this could be quite useful at times.