Well, that's why I said it really depends on where you live. True, the cop has to be stationary in order to utilize laser gun.
The problem is, in NJ where I live (the state chosen to be #1 laser use state according to Radardetector.net), there are so many spots for cops to be, literally every mile on major highway. So, either get laser protection, or just drive slowly. Never drive alone with radar.
On the other hand, PA, which I suspect to be OP's state, is pretty much free of laser use, so there shouldn't be much laser related issue. It's really YMMV.