Leupold builds a fixed 12X target scope. That would be a good one in my opinion.
If you want to fork out the big bones for a higher end scope. Steiner makes a 3-13 tactical and there is always the S&B PMii 3-12
He has no choice if he follows the rules. Just turn it down to 12X and keep it there.Hopefully a match director will tape and sign the magnification ring to ensure no tampering with during the match