They won’t be arrested if they are obviously American. Speaking good English and having valid ID and home address would likely make any encounter a minor inconvenience; minor, that is, to all except the open-borders crowd. Good citizens should not take offense to this law.
Frankly, I don’t trust this Mayor Gordon. Let’s see if he’s got the papers to back up his mouth ~ bet he doesn’t!
Even if you happened to forget your i.d., the other factors would easily clear things up within a moment or two. A lot like going through the border checkpoints in Southern Arizona. “Are you a U.S. Citizen? What’s you’re birthdate?”