It's a dangerous precedent, and I feel saver in the knowledge that such restrictions would be against my country's constitution. With that reasoning ("it's potentially lethal"), you could regulate a great many other activities and behaviours which I'd consider protected by personal freedom – like what kind of food you're allowed to eat or which means of transportation you're allowed to use.
Which is, in fact, something the hard left has been demanding for years, I might add. Whilst they're at it, why don't they just pen a law that forces obese people to lose weight? Cardiovascular diseases kill even more people than lung cancer. This is not good. Not good at all! What say you Kiwis around here, is there a chance this law could be struck down by your supreme court?