The ones that wander into my live trap get spayed/neutered, gives em somethng to think about. Still have one too smart for me so ffar.we have several cats around and every once in a while a mean cat comes around. Sometimes they are just hungry and try going thru our garbage.
But our cats come first so I keep a live trap handy and bait it with some canned cat food and trap the bad cat... Usualy a time out for most of the night cures them of coming around...In the summer they get a free bath before I let them out of the non harming trap.