You can't tell private establishments how to do business. I don't understand how the government has the power to do this.
Let's be clear, here, because I have debated this with nanny-statists many time in the past, back when DC was going non-smoking...
...the government has clearly established a precedent for telling businesses that are open to the public what they must do and cannot do. Health codes. Fire safety & egress codes. Building codes.
The reason I bring this up is because I am anticipating someone on this forum to use this as an argument in favor of the smoking ban. Many nanny-statist smoking-ban-supporters use this argument freely. And so I mean to cut them off at the pass before they can even attempt to start arguing with you that yes, the government can and does tell businesses what to do, even though they're "private" businesses, in the interest of public safety.
The obvious hole in this line of reasoning is that things like fire safety, health safety, building safety, are hazards that are not easily observable to the casual customer. When I enter your restaurant, I can't be expected to know that the egress door in the back is blocked with crates and thus, if a fire breaks out, I might not be able to get out. I can't be expected to know if your chef is not washing his hands and is possibly passing on harmful bacteria in my food. I can't be expected to know if the ceiling joists above me are sized and spaced in such a manner that the roof is safely held up. All of these are unknowable hazards, and so you can at least entertain an argument that the public (in the form of a governing authority) has an interest in protecting the casual customer from these unknowable hazards.
Smoking does not fit this bill, however, because it is a clear, obvious, knowable, observable hazard to anyone who can see and/or smell, prior to entering the premises. Not only that, but unlike a fire safety hazard or a health safety hazard like e. coli, second-hand smoke takes prolonged exposure to manifest itself as any meaningful harm. So you would have to observe the smoke, then make the conscious decision to expose yourself to it for prolonged periods of time (several years, regularly) to see any meaningful damage to your health. All it takes is one fire or one poorly-designed roof structure, or one exposure to e. coli, in order for me to be harmed in a meaningful way.
EDIT: ha, I knew it was only a matter of time...
And every bars becomes a "public" place when they open their doors to the public.