Why did they believe you threatened to shoot your cat?
I presume this is a firearm that you do not need a licence to own?
On the face of it, I’m not sure they do have power to seize then.
They can seize anything that they reasonably suspect will be used in the commission of crime. They do need some of evidence of that and I’m not sure they can really prove this.
However, the fact remains that they are refusing to return it. If you went to court then probably you would succeed against them but it is the time of thing that might be more expensive than it is worth.
They cannot deal with it by revoking your firearms licence because you do not need one.
You could sue at the small claims court for the actual value of the item. That would be cheaper.
If you are intent then your only option is to lay a complaint under the police property act.
Can I clarify anything for you?
Yes, as I said, they can seize if they have reasonable grounds to suspect an item will be used to commit an offence.
Yes, it could be a public order offence.
But that won't be the issue.
The issue will be that they will be saying you may have used it to actually harm the car and that would be an offence.
I'm very sorry but I am not able to confirm that there is no potential offence here.