I'm writing this as a way to make sure the law in the United States is abundantly clear and also that I'm not casting judgement. I do want to make sure things are laid out clearly in an official thread....
This Post focuses on the idea of "race radios" for Baja Races that occur in Mexico. However the intent extends to using non FRS/GMRS type accepted radio on the FRS or GMRS bands. The same rules that apply in the case of Baja Race Radios, are practically identical to FRS or GMRS radios.
I'm going to add a quote here from the post, which happens to be a quote from the FCC Directly.
Q: Do I think having FRS/GMRS frequencies programmed into radios you take into the wild is a bad thing?
A: No, I do not.
Q: Do I think transmitting on those frequencies, even at low power when loss of life, or severe injury isn't at risk is ok?
A: No, I do not.
When Life or severe personal injury are the case,
All Bets Are Off but otherwise you run afoul the rules and regulations set forth by the FCC, and I can't advocate as such in a public setting without at least making it abundantly clear.