How so? Multidwelling stuff.. (apartments and what not) would be the easiest of all..
the cops show up.. go to the basement.. turn off your $1.24 3" valve.. then they come up and knock politely on your door..
You can flush anything you wish.. but if we have a valve in there someplace we will catch you.. WITHOUT killing you and your children...
So now you're going to require existing buildings to re-do their sewers? Who pays for that?
Not that I don't appreciate your underlying concern, but really: the idea is unimplementable.