cinder, yrs ago, i set a boundary that i suggest that he called before he just popped up, that he couldn't come and if he came anyway then i would call the police, of course he didn't believe me and i had to prove that i meant what i said and called the police, he was arrested a few times, and after that, when he went out on a binge or whatever, he'd call before he came and if i didn't answer i guess he remembered that he just couldn't pop up. he didn't know if i would let him in or call the police so he'd wait until he could talk to me first.
since then, if he did call and i don't answer, he'd just know to keep callling or to leave me alone for a while then maybe months later he would try again, and if i want to talk i did and if i didn't i didn't. i guess you have to say what you mean and follow though on the consequences.