I believe you are wrong on the issue of feral cats. Our animal control traps them, then shoots them, the ones they cannot trap they shoot. I have been told by the local game warden that feral cats and dogs were open season. There are packs of feral dogs that have blended in with coyotes around here and we shoot them year round.
If noise is an issue use a .22 short. Gamo makes a whisper quiet .177 cal pellet rifle that is really quiet for a high powered pellet gun and it works quite well too. The only places you will likely be prosecuted for shooting a cat are big cities.
I got bit by one of them feral cats that had nested on my freshly washed and waxed truck. I got cat scratch fever from the piece of vermin, I just thought that was a Ted Nugent song when the ER doctor gave me a round of gobstopper antibiotics and some pain pills I knew it was no joke. Especially when I was treated for rabies. That vermin disappeared too even after the DNR animal control officer came in to kill it to test it for rabies. So maybe you should tell law enforcement that they can't kill feral cats. You know what the Humane Society does here, nothing. Animal control only keeps dogs 7 days here then they are euthanized. I know they don't keep feral cats. If a cat has a collar it is kept 7 days just like a dog, you pay the fine and bail Sylvester out or its the needle.
Feral cats are a major problem in America, (they are the #1 predator of birds), and there is NO major organization that is going to adopt them and take care of them, it simply cannot be done. A domestic house cat is three generations from feral. The third generation of kittens left unattended will be 100% feral wild.
I wish it were different too because I have a cat and dog and I do love animals but realistically they cannot all be pets or saved. If you grow up on a farm or in farm country you know this.