No, it is not illegal for a cat to poop on someone’s lawn. This is the general state of play on the planet. And it will seem an extraordinary situation to the person who owns the lawn where his neighbour’s cat has pooped. He’s got no remedy, he thinks. He is frustrated. He doesn’t know what to do. The word ‘illegal’ normally applies to criminal behaviour.
No specific law against it
The legislators (law makers) have decided that they should not legislate for the particular situation where domestic cats roam onto other people’s properties and do their business there. Legally speaking cats don’t trespass. Of course cats can’t be criminals and when a cat poops on someone’s lawn the cat owner is not a criminal either. It’s just one of those situations where there is no specific law governing this behaviour. Although in Europe, the EU commissioners decided that domestic cats should be kept inside to protect wildlife. It’s a theoretical proposal because it’ll never happen in reality unless something dramatic changes.
Of course, I’m referring to the world at large. There may, very rarely, be a town or city where they have a specific law against it but I would doubt that (there may be village in New Zealand where cats are confined under the local law). I can say with some confidence that across the planet the people who make the laws (the politicians, the people’s representatives) have decided that the citizens of their countries should work out the problem themselves in practical, sensible, decent and humane ways. I’ve underlined that point because you can’t harm a cat who poops on your lawn. That would be a crime, quite clearly.
People often quote the domestic cat’s “right to roam”. It is not written into law, quite the contrary. This right to roam of domestic cats exists because there is nothing in the law to stop cats doing it. The lawyers call it a lacuna which means “an unfilled space; a gap”. There is a gap in the law as mentioned. Nothing covers cat trespass or cats pooping in people’s gardens.
The law on this subject seems weighted towards cats and the owners of cats who wander around the neighbourhood. It is. The lawmakers have deliberately left it like that because it’s the best solution as far as they’re concerned.
Just a quick note about living in apartments. When you live in apartments you have mutual agreements with other apartment owners under leasehold law. This will apply to most countries. Leases dictate how people can and can’t behave. It has to be like that because people are living very close together when living in an apartment. There will be rules on cat ownership and how people interact with their neighbours. Sometimes people on the ground floor of apartment blocks have their own small area of lawn or patio. If a neighbour’s cat is pooping on this patio they may have a right of remedy under the lease.
Tort of nuisance
There is one potential remedy for the person who owns the lawn but it is hardly practical and to the best of my knowledge nobody has done it. You could sue the cat’s owner in the tort of nuisance. You would have to go to the county court in the UK or a similar lower court in other countries and try and seek an injunction against the cat’s owner and perhaps compensation.
On the quora.com website somebody says that you can’t sue a neighbour if their cat is defecating on your garden. In my view, that is technically incorrect. You can look up the tort of private nuisance and see whether it fits the situation. It probably does but it’s not going to be very effective and the cost of a court case like this together with the disruption and resultant neighbour dispute makes this method of dealing with the matter untenable in my view.
So the only way forward for the “victim” is to take practical steps which is what governments want them to do. There are only two things you can do which is to talk to your neighbour who owns the cat or prevent the cat coming onto your garden. Talking to your neighbour often does not work and it may cause animosity. That’s unfortunate but it is a practical reality.
The best solution is to stop cats coming onto your lawn. I would not use a deterrent on the lawn itself. You’ll read about things you can put on the lawn to prevent a cat coming onto it but I don’t think they work. You will read about squirting water at a cat that comes onto a lawn. That might work. Making the place unpleasant for a cat in the nicest possible way without harming the cat may be a solution but it may be temporary. Another solution would be to build a fence around your garden which prevents a cat getting into it. That’s the ultimate solution but it’s obviously expensive and not a lot of people would choose that option.
Wider issues – wildlife
On a wider issue there is a general trend towards keeping domestic cats indoors full-time to protect wildlife, primarily. That of course would solve the problem if it developed into legislation. However, there are real issues with this because a lot of people object to it and there are enforcement difficulties.
Cat owner’s perspective
Looking at the issue from the cat owner’s perspective, it is hard for them too. If they let their cat go outside to roam freely as the law allows they can do little to control their cat. They may know their cat is going into their neighbours’ gardens. Domestic cats don’t know about human boundaries. They might not like the fact that their cat is upsetting their neighbour but they don’t want to keep their cat inside all the time. They can’t afford to build a cat confinement fence around their backyard. Therefore there’s nothing they can do about it.
The domestic cat is a free agent. They do have this independence and right under the law. Dogs are different because they’re more dangerous. It is illegal to allow a dog to roam around the streets and in backyards. There are laws against that but cats? No.