I could see a law requiring lights on, if they are parked in anyway, on the roadway, or somehow in direct line of view.
If they are off the roadway... what difference does it make?
They can park behind a billboard, in the weeds, or hide out of view any which way.... I've even seen cops standing on an overpass with a speedgun, and calling ahead to cruisers further up the road.
I am all for at least marking lights on... :thumbsup:
These blacked out units can sometimes spook the crap out of me, and make me slow down, even if I wasn't speeding.