Private businesses like bars and restaurants should never have been told they have to restrict smoking in the first place. If someone doesn’t want to be exposed to smoke they don’t have to work at or patronize the business. A sign at the door would work.
That was my solution, too.
A conspicuous warning sign that tobacco was smoked in the establishment, or that it was not to be smoked, posted on the door.
If tobacco-free, fines for violating that (at the owner's discretion), like a traffic ticket. Offenders could be 86'd.
If an establishment had the signs up saying tobacco is in use on the premises, either don't come in or don't complain.