If there isn't a law against it, I'm pretty sure they can lose their license. In my experience, the person your banging is the last person who should be tampering with your head. I think medical boards typically agree on that one.
ELAINE: He was my psychiatrist, you know. He knows all my patterns. In my relationships I always try to find some reason to leave, so as my doctor, he can't allow me to do this, so he's not letting me leave.
GEORGE: What do you mean - "Not letting you?"
ELAINE: He has this power over me, okay. He has this way of manipulating every little word I say. He's like a Svenjolly.
GEORGE: Svengali.
ELAINE: What did I say?
JERRY: Svenjolly.
ELAINE: Svenjolly? I did not say Svenjolly.
JERRY: George?
GEORGE: Svenjolly.
ELAINE: I don't see how I could have said Svenjolly.
JERRY: So maybe he's got like a cheerful mental hold on you.