Depends on what you consider dangerous. IF the rig has been modified for all band transmit, and the antenna is sort of matched, no harm done. If you haven't modified the radio, and its out of band, nothing will happen. Even if the radio has been modified, and the antenna is not matched, most modern rigs will fold back output power to prevent damage to the PA.
..As to the legality of such, this is a pirate board after all

+-RH