Regarding controlling a cat: Many people have cats that they consider indoor cats but when it comes time for them to “do their ;business” the cat owner puts them outside. They do not want to trouble themselves with cleaning a cat litter box, so they shove the cat outside to poop in the neighbors yard. It is the neighbors who need controlling in this case. Now, for how to stop the cat from pooping in your yard…there is a commercial product that can be purchased at a feed & seed store called Fox Urine. It works to keep away cats, squirrels and some other animals/rodents. My daughter has spread crushed red pepper on the ground where the cats “go”. This also may take a bit of time but the cats will go to another neighbors yard. The fox urine works immediately. Many cat owners are unaware (or don’t care), but if your city has a leash law there is a good possibility that the law applies to cats as well as dogs. They could be fined for letting their animal run loose. Call your animal control office to see if it applies where you live.