They shouldn't be allowed to put the sign up unless it's court ordered. I know this answer doesn't pass the vibes test, but it's how the law actually works. If

They shouldn't be allowed to put the sign up unless it's court ordered. I know this answer doesn't pass the vibes test, but it's how the law actually works. If you post a sign on someone's property without permission, you'll get in trouble for trespassing, vandalism, or both. So get a judge to issue an order. In a serious situation, they very well might.