Quite a simple solution..learn how to speak "cat'"..and just tell it."Hey cat..if you come in here agian I'm gonna put your nuts in a vice!" throw in the occasional .."PFFTT PPFFFFT" this will let the cat know your pissed off!. If the cat starts to argue with you..kick him in the junk!.this will likely work..or the cat will need therapy and will be gone anyways