A person aired this problem online. They say that although their cats are allowed to go outside the house and are free to roam around as they wish, they come inside to use the litter tray to go to the toilet. She wants her cats to go to the toilet outside the home for reasons of convenience. Should she do something and if so, what should she do?
Firstly, there are advantages to a domestic cat using the cat litter tray rather than going to the toilet outside. The advantage is that you can see your cat’s poop and pee which is not a great subject to discuss but it’s a good health check. Other experts would endorse this. You want to check whether your cat has diarrhoea or is constipated and these sorts of things. It’s just another aspect of cat caretaking which can help keep your cat in good health. If you agree this then the problem is solved!
If you insist on your cat going to the toilet outside, I think the best solution is to gradually move the litter tray, in stages, to outside the home in the back garden (backyard in America), to a point in the garden where you want them to go to the toilet. Provided the weather is dry (you can select your moment) you can leave a litter tray at that point for a day or two and then pour the contents onto the ground where you want them to go to the toilet. This will encourage them to use that area in the back garden as their future toilet. It’s almost bound to work. One thing that might stop it working is if they feel insecure in that area. They might feel insecure because a neighbour’s cat (or two) is hounding your cats. This is another and more intractable issue. It needs to be checked out. If it exists it would encourage you to re-evaluate and let them continue using the litter tray.
You should also clean the litter trays thoroughly and remove any odours to discourage returning to them. In fact you could also put them in a safe place to prevent access.
A lot of inter-neighbour disputes regarding domestic cats are a consequence of cats pooping and peeing on a neighbour’s well-tended garden. That’s the impression I get from reading the Internet. Arguably, it is advantageous that cats are using a litter tray rather than an area outside the home. Neighbour dispute are bad news and to be avoided at almost all costs as they seriously undermine the ambience of your home environment.
Some more on litter boxes