Cat trespassing can be irritating or worse for some people. I used to live in a bungalow with a garden and my darling Missie who was killed on the road outside the bungalow used to go next door. The next door neighbours didn't like it and I can understand that as he was a keen gardener. Cats can make a bit (but only a bit) of a mess in a garden sometimes. He simply made some noise and she came back.
What if he had put in place deterrents that caused injury to my cat? In the UK there are one or two things that can be done although the law is a bit of a mess on this. It is also untested.
The Occupiers Liability Act is designed to protect anyone who is injured as a result of the negligence of the occupier of the building or land. So for example, if I visited a persons house at Christmas and his staircase collapsed and caused injury, the person who occupied the house could be liable in negligence (the tort of negligence) and be required to pay compensation.
The liability extends to trespassers. A trespasser can, it seems, include your cat. For trespassers the duty of care is a little tighter. If the occupier knows that there is a danger and that your cat may come into contact with that danger and the risk is one that you could have provided protection against then the occupier could be liable.
Obviously if the occupier takes deliberate steps to deter the cat the test above is satisfied. Clearly if the human keeper of the cat accepts the risks knowing they exist then that would be a defence for the occupier of the property.
The best course of action is to take steps to avoid the problem occurring through preventative measures and dialogue. The rights of humans (your neighbour) is as important as those of your cat.
If you were forced to litigate on this expect a bumpy ride and an expensive one if you used a lawyer. Although this might fall under the small claims process. I would doubt if anyone would sue under this act in reality. It is too problematic. In general people accept that there is little that can be done in law against "trespassing" domestic cats. The answer is in dialogue. In North America, neighbors occasionally kill trespassing cats. That is cruel and against the criminal law in the UK.
Thanks to the author of the book Veterinarian Notes for Cat Lovers (for bringing this to my attention)
Photo copyright Paul Watson reproduced under Creative Commons