And it's up to the parents to say, "You are the child. I am an adult. You have NO power over me or, for that matter, over anyone. You only have power over yourself. I hope that you learn from my mistakes and choose to be *better* than me in this regard. If you have a problem with smoking, then don't smoke."
(Typing with hic-cups isn't impossible... only very difffficull-t!) ;-)
You remember the UN Convention on the Rights of the Child.