The prospects are not good for someone who feels that they are a victim of a neighbour’s cats fouling their garden. There is no specific law which states that cats cannot foul someone else’s garden or land. You have to rely upon the general law. Depending on the severity of the fouling a person might start a civil action in the County Court for nuisance. This is a tort.
If an individual person is subjected to the alleged nuisance they would sue in “private nuisance”. When the public are subjected to the nuisance the action would be in “public nuisance”. Public nuisance actions are normally instigated by local authorities. If a person starts an action of private nuisance then if he succeeds he may receive an award of damages and he may get an injunction against the cats’ owner. He would have to show that there has been “material discomfort” or annoyance. My gut feeling is that 99% of people or more would be very reluctant to start proceedings like this. They are rare. There is no guarantee of success. Unless the neighbor has a large number of cats and there has been a substantial amount of fouling such an action would fail in my opinion. There would be costs too and these might be expensive.
It is worth adding that cats can not trespass and have a right to roam but this does not mean that cat owners have a right to be irresponsible. The local authority might take action against a cat hoarder under the Environmental Protection Act 1990. Cat hoarding can cause a genuine nuisance to neighbours because of the smell and cats wandering around neighbouring gardens. Although if a person is asking about the law on cats fouling they will be normally be asking about one or two cats coming into their garden and not about cat hoarding.
The truth of the matter is that when a person feels that they are a victim of cat fouling they are in weak position in comparison to the cat owner. This is annoying to people. It can also lead to cat owners being a bit careless or irresponsible and the “victim” taking the law into his own hands (don’t!). Even though I love cats dearly and am an animal advocate, I do believe that cat owners have an obligation to respect the rights of neighbours. It makes sense to do so in order to create a harmonious neighbourhood. Not everybody likes cats or is able to tolerate cats defecating and urinating on their land.
There is one criminal aspect to this matter which is likely to fail as well in my opinion. You could claim that a neighbour is being antisocial. You could make an application for an antisocial behaviour order which is normally made by local authorities or the police. The applications are heard in the Magistrate’s Court. If you succeed in getting such an order then the cat owner would be committing a crime if they fail to comply with it. However, such application in my opinion would be unlikely to succeed and I’m sure that they are extremely rare.
Finally, you might consider talking with your local authority. You might wish to make a formal complaint to them under Article 8 of the Human Rights Act. This is your right to respect for your family and private life. In response they will probably argue that the cats’ owner has equal rights and the right to enjoy letting the cats roam onto your property. You could then argue that the council was in breach of Article 14 of the Human Rights Act on the basis that they were discriminating against you by putting the cats’ owner’s rights ahead of yours. This is a very fancy argument which may put some pressure on the local authority. It would take some confidence to carry it off, however. Personally, I don’t see it succeeding and would not recommend it.
The best way forward would be to try to convince the cats’ owner to respect your wishes. You may do something to assist in that regard by sharing the cost of building an enclosure for the cats but this is highly unlikely to take place because you will not want to part-fund an enclosure and secondly because the cats’ owner will not want to build one.