Pretty much all of it is wrong, the post is full of urban legends, not facts. Cops do not target license plates or headlights, they points at any spot of a moving vehicle, they target you hundreds of feet away. license plate covers do not help against a laser whatsoever, cuz laser is shot at the front of the car, half the states do not even have front plates. covers only give cops a reason to pull you over even if you did nothing wrong on the road. a ticket for a red light camera is 55-100 bucks, a ticket for intentionality obstructed license plate is up to 600, also depending on a cop you may be arrested for that too. depending on your behavior.
To answer OP question, if a laser hits you, it is too late for a warning, until a cop shots a laser at you there is no warning. They use IR laser, it can be jammed by a special jammer, I'm pretty sure they are illegal in all 50 states. When you jam a police laser it will return an error, but it wont tell that jammer is used, it could be due to bad aim as well, but I have little doubt if a cop has you clearly in his laser view and an error comes back, he is going after you anyway.
It is a lot easier and cheaper to beat a speeding ticket in court than an obstruction charge which they will slap you with if you get caught with a jammer.
The best way to get out of a ticket is to have another cop's pba/sba, lt.... card, cops give them to their close friends and a family members, 99.9% chance after showing the card, a cop will let off, unless you did something really bad, or that cop is a real a$$. I have seen cops come and confront other officers who gave a ticket over their pba card. they really do not like it, not without a phone call to a number written on the back of the card, next to your name, so do not try to use someone elses' card they do not like it even more,
You make an interesting point about intentionally obstructing a liscence plate, and the consequences.
But the question is, who's eyes are being effected by this?
Now the liscence plate covers that I am describing in no way obstruct a police officer's view of any licence plate on a car that he is either following, or that the officer has pulled over.
As a matter of fact, there isn't a whole lot of visual evidence that a police officer can obtain once he stops and approaches the driver side of a vehicle.
The licence plate cover is clear, but the translucent texture is hard to see with the naked eye, and at certain angles in certain lighting, it is impossible to see.
The only eyes that are effected here is the eye of a red light camera.
I know you are not suppose to believe everything you see, but I have seen demonstrations of how these license plates covers work to throw off red light cameras.
I think an investigative reporter for one of the major networks was doing a story on this some time ago.
So one could argue legally that obstructing a licence plate only applies to human eyes who are looking directly at a plate in real time.
This would not include an AI camera snapping photographs, that a few days later are simply put into an envelope from some anonymous employee at the highway department, which is then mailed to the perp.
This legal argument would classify these licence plate covers as legal via loophole.
To your point about where a laser can make contact with a car, and still record a speed limit:
I figured that headlights, taillights, and licence plates would be the primary target of a police laser gun, because they are simply more reflective, and relatively flat which insures that a laser's round trip takes the exact same path, to and from, which must happen in order to record a vehicle's speed.
It seems that if a laser hits a curved part of a vehicle, or any other part that is not flat, that it would redirect the laser back on a different course than it took on the way to the vehicle.
If this happens, a speed cannot be recorded.
