radar jammers are not legal.
if every laser jammer on the market is a shifter, then there is no such thing as a laser jammer and laser shifters are legal.
will the cop know you have one? yes, because you will be the only car on the road that doesn’t give a speed reading, thats how shifters work, cops don’t receive a signal back. can he do anything about it? yes if youre dumb enough not to slow down the second your shit goes off so he has time to switch to radar/visual/etc.