would tend to suggest that it would be illegal to use it without a FRTOL
PPL holders have an air-band radio operator license in order to qualify and so they can use an air-band transceiver.
Not strictly true!
The privileges of a FRTOL are to operate an aircraft radio station. If the portable transceiver forms part of the aircraft radio station i.e. in an emergency, it is perfectly legal to use it. On the ground away from the aircraft, the FRTOL is no more use than a driving licence, it is an operator licence not a station licence. Any transmitter, unless it is subject to an exemption, needs a radio station licence to operate it. There is nothingh illegal regarding posession or sale of such equipment unless it falls into a specifically restriced category such as some CB equipment.