That and a removable antenna. They are only legal to use on Ham Bands and Marine Bands.
IIRC, GMRS radios can have removable antennas.
EDIT: No, I'm wrong about that. Part 95 (
here), section 95.1787 says:
(4) The antenna must be a non-removable integral part of the GMRS unit.
Seems assanine to me. How would that work for a repeater, for example?