In some states you may run into what is called a "Home Rule" city. I believe that Denver is one such city, and the city laws can trump Colorado state laws. I don't know how you'd find out if your city is a "Home Rule" city, or if you happen to be traveling to or through one. Google or other search engine, perhaps?
It should also be noted, that although the FCC has issued its' statement that licensed Amateur Radio operators are exempt from anti-scanner laws, and many states have codified this into their own laws, IIRC, this exemption ONLY applies to Amateur VHF, UHF, and/or multi-band transcievers that have incidental out-of-band reciever coverage of public safety frequencies. It DOES NOT apply to a licensed Amateur Radio operator who is in possession of a scanner radio.
It also does not apply to a licensed General Mobile Radio Service (GMRS) user who may own a new or used UHF land mobile radio that may be the same exact model used by local law enforcement, or which may be similar in appearance.
So, it is possible that a law enforcement officer could cite/arrest an ARS licensee, and confiscate the scanner(s) in their possession, and a prosecutor could attempt to prosecute the case with a judge's permission. For the GMRS licensee, a law enforcement officer or prosecutor may argue that the radio is capable of being programmed to a police or public safety frequency, especially if the licensee has a computer and the software to do so with them.
I'm not saying it has happened, and I'm not saying will happen. I'm saying the possibility is there. So, I would simply exercise caution in any state where an anti-scanner law is on the books.
John
ARS KB7MIB/GMRS WPXJ598
Peoria, AZ