Some years ago our (ACT) EC issued a breach notice to a unit owner about a fence that had been erected without permission and enclosing an area of common property well beyond the unit boundary. Some previous ECs had tried to deal with it and got nowhere. [In their defence they were dealing with an earlier version of the Act that had less clear processes for dispute resolutions.] The unit owner ignored the breach notice but soon after put the unit up for sale.
We wrote to the owner that removing the fence might help to avoid problems that a potential purchaser might have getting a loan because banks would want to know if there were any unapproved alterations. We also wrote to the real estate agent including a copy of the breach notice and asking him to advise any purchasers who seemed seriously interested that the fence would have to be removed and that the unit area was actually smaller than the enclosed area suggested. We put a copy of the correspondence on the records where they could be found. The real estate agent was very good about it. He checked with the EC to make sure he understood exactly where the unit boundaries were, what kinds of fences could be approved and where. The people who bought the unit took down the ugly, wrong-sited fence promptly, enquired about putting up a new fence of an approvable sort in the right place but in the end preferred the view without a fence and landscaped the area very nicely.
If you are sure of your position and deal openly with all concerned, I think good outcomes can be achieved, particularly at the time of a unit sale.