Such systems can only work with cameras, and all it takes to defeat a camera is spray paint, paintball gun, of if you are worried about being identified.. a drone armed with a small pressurized canister of paint.
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They rely so heavily upon the average citizen to be law abiding, and they wouldn't be able to keep up if even 1 in 10 people destroyed a camera every time they detected one. Police States are expensive and require fear to keep people in line. They would have to start shooting people for camera vandalism, and so far, we can still shoot back if they start doing that.