sfb88, to answer your off-topic (but not too far off) question, it really is on a state-by-state basis, with most states having an exclusion to the law for FCC-licensed amateur radio operators and media journalists. I drove with scanners up on my dashboard in a big rig in all 48 states for 17 years and I was only hassled a few times, once in Providence, Rhode Island, and at a weigh-station inspection in Redding, CA. A state trooper in Elizabethtown, KY confiscated my 396XT once and I had to go to court to get it back. Which I did, at a cost and sacrifice to me of about $700 in lost work and motel bills. That trooper left the courtroom with a pretty red face, I will say that. I think my face was a bit red, too.
Yes, most states have amateur radio operators written into the law with consent right along with EMTs, emergency personnel, media journalist and new teams.
EDIT: some states differentiate between installed scanners and portable scanners, too. I am not up on those statistics as I do not drive anymore, but I would like to know from someone here who might know, which states do not recognize licensed amateur radio operators to be excluded from their state scanner laws?