Hi,
The best way to resolve this is through having a by-law.
It can then be used for preventing abuse of common property, initially through Notice of Compliance and then through NCAT.
Strata Schemes Management Act 2015 sets out the steps in section 146. It requires that a notice to comply must be in a form approved by the Secretary (which is, for this purpose, NSW Fair Trading – one can download a notice to comply form from their website).
In regards to asking local council for help, that is more complex. It can happen but it is not the best or most efficient option.
We have personally been involved in forcing City of Ryde Council to take action against large strata complex who allowed, without approval, parking on public land behind the complex. Basically, a group of owners and tenants illegally used public recreational space for parking (officially named “Unnamed Park Lot 202 DP848752, 440 Lane Cove Road”). It took us significant time to get Council to act but we won in the end: Ryde Council Reference 2158948.