Sure, that's up to you!
As soon as you are admin you can:
/set username BNET\auth_joinnormalgame 1
/set username BNET\auth_joinladdergame 1
/set username BNET\auth_createnormalgame 1
/set username BNET\auth_createladdergame 1
Also make sure his password is not compromised before you do that