If this is the case, then it's probably how the module is written.
You would have to probably modify it by making a check in code that the user who they are banning is not member of the Group # 1, which is the Webmaster Group.
Am I on "ignore" status?
i just don't understand why don't XOOPS developpers import them?
at present cbb is not working correctly with 2.3.3