Using Charm Person spells on PC's, like to hear your thoughts...

[Mouseferatu]

I'm with everyone else. Charm is part of the game, pure and simple. Like with anything else, it gets old if it's overused, but it's absolutely an appropriate anti-PC tactic in the right circumstances.

As for how I "enforce" it? I don't have to. My players understand the concept of playing in-character, even when it means they have to do something they wouldn't. Occasionally I need to offer an FDR (Friendly DM Reminder), but never more than that.

 

[Voadam]

Playing in the banewarrens my witch hunting wizard ranger got charmed by a vrock.

So I talked with him, got a warning about the devils who were unleashed and running around and then he disappeared when the rest of the party came around. He had attacked the arcane trickster by surprise before and done a lot of damage to him. Still I almost convinced the party paladin we needed to ally with the demon against the more powerful devil. I also got him to agree that we couldn't then betray our ally and kill him if we made an alliance, as we are the good guys. The arcane trickster got fed up as the paladin was seriously considering my proposal and dispel magiced me breaking the charm.