Law enforcement is far from a private retail store.
Law enforcement is employed by the gov't and here in the US, that means they can't watch us without a valid court subpoena. It is one thing if the LEO ( Law Enforcement Officer) catches you speeding up a road while you are stupid enough to go by him/her. That is just stupidity. You get what you deserve if you are stupid enough to do those sorts of acts.
If they want to put cameras up in public just to "monitor" people's activities, that is "Big Brother" style of governing, and far from legal in the USA, in my opinion.