Darter, I understand she is frustrated but trapping pets and giving them away is not the answer. you can't keep a cat indoors, they are outdoor animals and can't exactly tell them not to go in to other people's gardens, listen to people's suggestions how to deter them but don't resort to those measures.
Just why is it you think that that is acceptable?
If you cannot control your cats (which is a silly statement, as no-one can control their cats), then you cannot allow them to leave your house. And if you cannot accept that they must be in your house 24/7, then you cannot own cats. Simple as that.
At least the measures Maudi is proposing are humane and don't endanger the lives of the cats. If I had her problems, my precautions might be less so, especially if I had small children.