Originally Posted by rondocap
Nope, they actually block the laser signal and jam the laser gun. Then when you've slowed down enough, you turn it off with a switch and the laser gun gets a read on your now (slower) speed.
It's legal in most states, you'd just have to check if it is in yours.
So I assume it's always on until you turn it off and the cop reads your lower speed? Also, can't you just leave it on and he'll never pick up the speed?