They are legal as long as you do not transmit; hence "scan only." Radio Shack has a ton of scanners at every price range you could want.
Well, I wouldn't be quite so sure about that. You do need to be a little careful about WHERE you are (what State), in what sort of situation - i.e., standing outside with one, or in a vehicle with one. There are various State laws that govern use of scanners, and you probably ought to look at those, especially if you want to use it while in a vehicle. Some States ban them outright, unless you have a ham radio license from the FCC or are legitimately a public service (police, fire, etc) officer.
For instance, in Florida (and this is a CRIMINAL Statute):
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843.16 Unlawful to install or transport radio equipment using assigned frequency of state or law enforcement officers; definitions; exceptions; penalties.--
(1) A person, firm, or corporation may not install or transport in any motor vehicle or business establishment, except an emergency vehicle or crime watch vehicle as herein defined or a place established by municipal, county, state, or federal authority for governmental purposes, any frequency modulation radio
receiving equipment so adjusted or tuned as to receive messages or signals on frequencies assigned by the Federal Communications Commission to police or law enforcement officers or fire rescue personnel of any city or county of the state or to the state or any of its agencies. Provided, nothing herein shall be construed to affect any radio station licensed by the Federal Communications System or to affect any recognized newspaper or news publication engaged in covering the news on a full-time basis or any alarm system contractor certified pursuant to part II of chapter 489, operating a central monitoring system.
{emphasis added}
... ... ...
(3) This section shall not apply to any holder of a valid amateur radio operator or station license issued by the Federal Communications Commission or to any recognized newspaper or news publication engaged in covering the news on a full-time basis or any alarm system contractor certified pursuant to part II of chapter 489, operating a central monitoring system.
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So if you have a scanner in your vehicle in Florida, to be safe from prosecution you really need a ham radio license, if you're not press, an alarm system contractor, or in government. Most scanners, right out of the box, automatically cover the frequencies "assigned by the Federal Communications Commission to police or law enforcement officers or fire rescue personnel of any city or county of the state or to the state or any of its agencies".
Now, the purpose of that statute is probably to penalize anyone, like a burglar or armed robber, who uses a scanner to try to keep from getting caught in the act, or to evade capture. But the statute doesn't discriminate, and the unwary scanner listener who happens to get some police officer ticked off for some other perceived threat or perceived bad behavior, is likely to find himself cited for that criminal violation as well.
By the way - ham radio licenses do NOT require knowledge of Morse Code any longer, so if the Morse Code requirement was putting you off from getting a ham license, you no longer have that excuse available