Unfortunately, just because they sell them doesnt mean they are not illegal. I use to have one of those neon licence plate frames on my car. I got pulled over twice (in two different states) because they said they were illegal. I had a purple one (to match my car) and they said that if I had a red one, it might be ok.
I think the key is to look and see if it says anything like "For Offroad Use Only".
Soren
