Not sure what you mean about "bylaws" in terms of keeping chickens who no longer lay?
I can't see why there would be any ordinance regarding your private pet issues? What about dogs or cats who are too old to reproduce? Same thing.,
In terms of "older hens" I think it is a personal preference. I'm a backyard, suburban chicken owner. I don't harvest my chickens, just the eggs. All of my chickens have names and they are my pets.
I have one hen, Hannah Banana, who is nine years old. I can't tell if she lays eggs, but she broods two to three times a season. I have a few others who are five years old. I see them sitting on the nest fairly often.
Bottom line: In my world, they live until they die. I love them all and do everything I can to keep them healthy and safe. I know I'll be extremely sad when the day comes. For now, they are active and happy.
That's all I want.
Geri