Our maverick member has now been banned and all our Moderators are aware of the situation.
We Moderators will obviously have to manually deal with any further attempts of sneaky piggybacking onto active members' posts by this banned party. If we are diligent and can catch things before they get approved then the banned party should eventually give up trying to sneak material onto our group.
Again, thanks for all the suggestions. They have been helpful for clarifying how we need to proceed wth this situation.