Is it truly unlikely? I live in a university and it is pretty common to see illegal lockout calls in the police log. I can't speak for OP but in my jurisdiction a landlord who performs an illegal lockout can be penalized $100/day, have to pay compensation for lost/damaged items, pay the tenant's legal cost and even "emotional distress" if the judge is cranky enough. It just isn't worth it. Especially if OP's friend wants to become vindictive.