I don't think laws are the best way to get people to quit smoking (drinking, doing drugs, having sex, eating, etc). Tax disincentives are a win-win kind of solution. The government gets money and the public has a reason to talk about the "sin" so people are more informed of the risks to their health.
The real best solution though is probably better education. Of course, you have to get the message before you start, because afterwards you are addicted and it's next to impossible to just quit.