Trap it. Water it. Let it go back to its owner. Do that a few times. It will sooner or later get the idea. Otherwise, call your animal control people and have the cat removed. It isn't nice to kill people's animals. However, it isn't nice of people to allow their 'pets' free range of the neighbourhood. It's either a pet or it isn't. If it is, the owner has a responsibility to ensure it doesn't become a nuisance to you. Take Mark Twain's advice about getting a cat to eat mustard. It will ever after stay away from your property.