I think banning smoking is consistent with the principle of liberty when smoking will pollute the the air that non-smokers breathe or when smoking will pollute property with discolouration or odour against the owners wishes.  In that tobacco smoke is irritating for most non-smokers, it is a form of assault.  In that tobacco smoke can damage property, it is a form of vandalism.

Some business owners have said that they should be able to allow smoking on their property.  They obviously don’t care about the odour which is acceptable.  Exposing customers to the polluted air is not acceptable.  If the form of assault was more immediately violent as with a blunt instrument, it would be more obviously unacceptable.  The principle is the same in both cases where a person’s liberty has been violated.

In a free society, a person could choose to smoke and the responsible smoker would be respectful of non-smokers by not smoking in places that will affect the air quality of non-smokers or that will stink up other’s property against their wishes.  Irresponsible smokers who show no respect for others or their property would be held accountable with some form of consequence.