If we're going to use Unfair Acts, which I would agree seems to fit pretty well here, why not be a bit conservative and use "The referee may take any action he considers equitable, which includes directing that the down be repeated ..... etc", and enforce a 5 yard penalty and replay the down? If they do it a second time, 15 yards and loss of down.
I'd have no problem at all justifying that with my supervisor.