In the US and Europe, radar detectors are legal due to the fact that radar detectors only provide the driver with information, just like a GPS navigation system.
So, what does a radar detector behave? it basically scans for signals given out by radars and provides (on display or sound) the distance of the intercepted signal (radar) and it's clocked speed (some models). It does not, however, cut/disturbe/interfere with the radar's signal at all. Some models of radar detectors do this, which IS ILLEGAL worldwide.
But those other models, are they REALLY legal? if police stop you and notice what you have, any fines, confiscation or even impoundement of the vehicle?
I want concrete proof/answers