Ask a Canada Law Question, Get an Answer ASAP!
The Board cannot do this on their own.
They would have to bring a motion to the members and have that motion pass by 80% of the owners.
If 80% or more of the owners agrees that the by-laws should be changed and the building must be smoke free and even ban smoking in the units then this by-law is lawful so far and there is no requirement that the current owners who smoke be grandfathered in.
So it is possible given the current state of the law that this can happen.