If he really wants to prevent them from "tarnishing Nigeria's image" he should attend to them when they return home on their periodic visits.
(And check that chief's ID, it is just possible that he gave you a false name and address!
British Investment Trust Bank" which (had) a website which talks about customer security and uses pictures of tourist sites in London to underline its respectability and status. As of 18th July '03, both of these websites are unavailable.
Strangely enough, this "bank" does not feel able to publish its correct address. We must thank both British and American enforcement agencies for their rapid reaction.
Apparently the President of Nigeria has declared "total war" on the 419 scam artists and said that they shall have "no hiding place".