A term usually given to normal members of the public who find it amusing or funny to imitate police cars by attaching some form of beacon to their car in the hope of making people believe they are in fact the police. Often this hobby (as some people make it) takes place at night, to add to the illusion of the beacon.
Driver: 'Hey who's that behind us? They've got a blue light flashing, should I pull over'
Passenger: 'Nah, it's just beacon bandits, keep going'.