The problem with an active radar jammer is that its use is a federal felony (violation of FCC laws, basically transmitting without a license) and probably a local misdemeanor (interfering with a police officer in his lawful duties). The FCC does not have jurisdiction over laser frequencies, but using an active laser jammer would be just as much of a misdemeanor as an active radar jammer.

Most modern radar and lidar guns have some level of active jammer detection, so it isn't necessarily an uncatchable crime either.

Since I happen to be working at the company that invented radar, I have a vested interest in avoiding any felony or misdemeanor charges, much less any convinctions.