First thing, they had terriers, spades and collars (guess they meant radio) but no ferrets. So they were probably not rabbiting.
Police probably know that but could not prove it.
Add to that a badger set was said to be disturbed.
I think if you was to do a bit of discrete ferreting, dressed like you know what you are doing, in Surrey at least you would not end up in court.
They come of well I think, except for the criminal record, couple of hundred quid fine and even kept the dogs.
Not saying they deserved it but that is the stupid law in action.