What is more important, the idea of choice alone or being indicated the right course of action by law, outlawing the immoral choice?

For example, a smoking ban in public places in the UK.

Would it be more prudent for someone to make the choice to be allowed to sit in a room of smokers, knowing they had the choice to do so but also knowing it's going to kill them (or at least adversely affect their health in the end) or is it more appropriate to be told by a central government that you cannot smoke in public places thus keeping all non-smokers safer?

The second point relies largely on the idea that people will not make an informed choice of their own. Vested interest will get in the way. Either a business will want more custom and allow smokers, affecting the health of other patrons but who cares because profits. Or people will ignore health warnings and enter anyway, thus requiring someone to tell them not to do it but affecting their "free will".

Meh!