Apart from get a dog?
I cannot help with the legal and strata by-law side of things in this area but:
Google natural cat repellents, that you can spray around your plants without affecting the plants. You do not want something that will possibly kill or make the cat sick that may just cause more problems than it is worth
A few things I can suggest:
- Put a chicken wire fence around the plants. Probably more trouble for you than it is worth.
- There is a plant called the Coleus Canina which is a natural cat, dog and fox deterrent
- You can buy a product at Bunnings called Skedaddle Dog and Cat Deterrent costs about $15. It claims to be non toxic, effective in all whether and can be used on gardens, lawns.
- You make a natural repellent from vinegar and herbs. (google it and you will get tonnes of pages.
If you have a dog and so not want to deter your own dog, then cats dislike the smell of citrus.