Good point, CBF, but it depends on the by-laws. They may only specify dogs to be carried or taken on leashes .. or not say anything at all. That's the wonder of by-laws … they're little fortune cookies of mystery.
Let's assume kitty is allowed to wander – for the sake of a delicious argument, if nothing else. What then? Is this cat-napping? Or slightly over-zealous kitty care?
If it's not a breach of by-laws, it's not a strata issue. But then, a solution is still required.
I had an over-fed cat who developed diabetes. Twice-daily injections for umpteen years, expensive cat-sitters when we went on holiday, constant trips to the vet. And all because we fed her a bit too much.
It's a worry and I don't know if there's a solution.