With a military radio, let's say an AN/PRC-117G, I could program it anywhere in its frequency range (30 - 2500 MHz), obviously sticking to frequencies allowed to me. I see that in the commercial/amatuer/family radio world, the FCC frowns on that sort of thing.
True except for ham radio, where you can use anything that meets purity and bandwidth specs for whichever band you are using. So if you had such a radio (and a ham license of course), you could legally use it on 6M, 2M, 1.25M, 70cm, 33cm, 23cm, 2300-2310 MHz, and 2390-2450 MHz.
As for GMRS, any radio that was originally Part 95 classified and still meets original specs would be legal.