Of course moth balls and cayenne are harmful if eaten or gotten in the eyes, but a cat is not going to be stupid enough to do either of those things once they have been laid down. If the remedies work they aren't going to get close enough for it to happen accidentally even. Keeping your own cats out of neighbors yards is impossible since they can jump over fences, etc and there is no physical way to control their wandering if they are allowed outdoors. It's not a matter of what we "let" them do. The people who think cats should be "controlled" by their owners, or not brought into the city at all are simply showing their bias against our furry friends and their insensitivity toward those of us who love them, not to mention their ignorance as to the reasonable and responsible care of them. My problem is keeping my own kitty (and only one of the three I have does this) from using my vegetable garden as a toilet. The rest of the yard is fair game. I simply don't want her constantly digging up the seeds and sprouts while doing her business. I think tucking moth balls into the corners of the garden where they will been smelled and not seen seems like a smart option.