I am truly not trying to be argumentative, but to just understand. What federal law? I don't expect you to cite a statue, for example, but can you clarify, is this an FCC thing, or a department of commerce thing protecting copyrights (like pay per view TV, for example)? Maybe its more like the MP3 download software.... it isn't illegal to produce or use the file sharing software, it only becomes illegal if you use it to download copyrighted material...
Perhaps its an FTC issue with patent-infringement assuming the encryption technology is patented. But if you independently "discover" something that someone else discovered first, that isn't illegal, unless you exploit their technology without their permission, or paying royalties etc etc. Complicated- yes. And patents DO expire. I imagine that "once upon a time" GE's original EDACS stuff was proprietary, and perhaps even Moto's trunking, but look how that's proliferated.
so again, it is actually illegal to manufacture and/or own a decrypting scanner (or decrypting software), or does the illegality arise of what you do with it?
BTW-I think its inevitable that a decrypting scanner and/or some hacker's software will emerge that can follow encrypted systems. I think there are too many radio shops and radio techs out there that set up and program new radios that go on line to expect all that proprietary stuff to stay bottled up forever....