Imagine you have a shop window, your shop is closed - lights on all the time, burning electric as it is your advert to the customer base, showing your wares.

Now if you add a sensor to detect if somebody is looking in your window and turn the lights on in the window - only when somebody is looking. Well, you would save electricity in lighting usage.

However, you detection system would be a surveillance based system t0o aid advertising of your wares.

So any ban - needs to be well defined. Defined as identifiable surveillance, else small edge-cases like this will potentially fall foul.