Enforcement of the by-laws is optional in NSW. However, an owner or even a tenant can apply through Fair Trading for mediation or for the issue of a Notice To Comply (the instrument by which by-laws are enforced) against another owner. After that they can go to the CTTT for adjudication. A tenant can even apply to Fair Trading to force their landlord to make an application for a Notice To Comply.
ECs have to vote on the issuing of a Notice To Comply but if Strata Managers have the required powers delegated to them by the owners corporation, they can issue NTCs if they think there is a valid complaint.
By the way, a Notice To Comply is just what it says on the tin – it's a warning to stop doing what you're doing or face the consequences … which may be a fine at the CTTT if they don't comply.
In other words, it's an official warning. The EC or strata manager doesn't have to issue any prior warnings (although that is one way of letting people know there's a problem they might not be aware of.)
If you feel your EC is being run for the benefit of individuals on it, and to the detriment of everyone else, you can apply to have a statutory manager imposed who will take over the running of the building in place of the whole Owners Corporation.