COMPANION ANIMALS ACT 1998 - SECT 16 Offences where dog attacks person or animal
dogs must not harass etc...
In this particular case, the dog had no way of knowing the people provoking it were not trespassing and defended itself. It does get a bit blurry when the dog attacks someone who is invited onto the property or lives there. Ie the owner should take steps to prevent dog from having any misunderstanding about an invited person's intentions.(2) It is not an offence under this section if the incident occurred:
(a) as a result of the dog being teased, mistreated, attacked or otherwise provoked, or
(b) as a result of the person or animal trespassing on the property on which the dog was being kept, or
(c) as a result of the dog acting in reasonable defence of a person or property, or
(d) in the course of lawful hunting, or
(e) in the course of the working of stock by the dog or the training of the dog in the working of stock.
It also gets a bit blurry about what is reasonable. A warning growl - is reasonable. Mauling someone and not stopping when told probably isn't. I might be a bit late telling my hound to stop mauling a home invader, but I can't imagine she'd do anything either. I could be wrong.