Is Radar Detectors legal for private cars?

You ask if radar detectors may be used in private cars. That depends on the law of the state in which you are driving. Most states permit it. A few (one of which is Virginia) do not.

According to one web site [you should go and read several to be sure], in California they are legal for all vehicles except commercial vehicles weighing more than 10,000 lbs, but they can not be attached to the windshield if a police officer thinks it might block your vision [since the officer will not like your having one, they would probably find it does block your vision or act as an illegal distraction; you can attach it to a sun visor but I suppose they might still say you were distracted so not driving safely]. Use can not have them on while on a military base. Two east Coast states ban them but they are okay under a Federal loop hole, but radar jammers are not. Unless you have a special type, the officer will know you have a detector on.

That depends upon the jurisdiction you're in, radar detectors are illegal in Michigan, bud, for example, they are not legal in Canada.

It depends on the jurisdiction. I believe that state wide they are not legal. Think about this in a positive way; the cop is in a closed environment (his scout car) with a radar device that emits high energy microwaves. The radar unit is in a cheap, plastic box with a minimal amount of shielding in order to keep the costs down. You may get a ticket, but he could have some long term health issues from the radar. Vengence is a dish best served cold.

No.