Log into the router and disable it? Odds on the password is something like password or admin or whatever.
Failing that, change the mac address and the router will see it as a new computer, and probably default to no controls.
Of course the correct answer is that you should punch him for being such a twat that they had to do this.
If he'd been responsible in the first place they'd never have bothered. Bypassing it is just proving them right, I hope he gets caught and they confiscate his PC.