In NSW the Owners Corporation in not obliged to enforce any by-laws except for those relating to maintaining the fabric of the building and common property. Pursuing smokers (or party animals or mad barbecuers) is entirely at the discretion of the Executive Committee in the first instance and ultimately the Owners Corp as a whole.
Fixing balconies, lifts and common areas, for instance, is not optional (although it effectively is until someone kicks up a stink). The reasoning is that if you have an issue with smoke or noise or whatever, there are avenues through which individual owners and tenants can pursue their case.
My own building, for instance, actively pursues anyone who installs air conditioning (except on the three floors where it is allowed) but, despite ensuring everyone else has to cool their apartments by keeping their windows open, does absolutely nothing about smokers and barbecues on balconies. Is it right? Does it make sense? No – it's strata living where the over-riding principle is all too often “I'm all right, Jack”