I really don't think that's necessary. Just by having reasonable proximity to Public trashcans radically reduces littering. Some level of perceived enforcement

I really don't think that's necessary. Just by having reasonable proximity to Public trashcans radically reduces littering. Some level of perceived enforcement is required, but in reality it just needs to be a sign with a high fine on it. And finally some level of public funded cleanup groups and you can get pretty far with keeping spaces clean.