It has been my experience that Narcissists only understand two things when it comes to boundaries: Force and Consequence. They don’t care about you, so they do NOT respect your boundaries. You have to be forceful (blunt) and present a consequence (e.g., going to jail) to thwart them from their evil action(s). Check out Dr. Carter’s video below where talks about blunt communication.
Psalms 82:4 Rescue the poor and needy: Deliver them out of the hand of the wicked.