All you have to do is turn the ignition to position 2(run) press ARM button and it will reset the immobilser, allowing the igntion lights to come back on and then to start.
If it does not do this I would check where he has taken the power feed(igntion from), on my C5T2, I have to re-arm dis-arm thing but it is on a vauxhall with no accesssory live from the ignition switch.
tabetha