In that last case, where you have asked them to leave and not come back... but they do. There is a thing called a citizen's arrest. Allowing nonpolice to make an arrest and detain a person. But what the law says and what you can do is often not the same.
I just imagined haveing your doorbell record you saying to never come back, then slapping handcuffs on them if they do. Kinda sounds like fun.