Stray cats being fed by owner

How can we stop this? The Canterbury Bankstown Council rangers advised that unless they can see a person putting food out or feeding them they cannot take any action. Compounding the problem is that NSW law allows cats to “roam”.  Strata have a sign up saying no cats, but my guess is that nothing strata can do will deter this individual owner. Without going into it, the committee is slowly getting on top of cleaning up a very dilapidated and dirty common area. We recently got rid of a very large tree which was home to roosting ibis above clothes line area. Now we are onto the next “wildlife” issue.