I think (I could be wrong here) what you're talking about is moderating groups. Natively, the only way to do this is to go to the security setting for the group doc and list only those people who can send to this group as readers. However, this will only prevent the other people (the ones you don't want to send) from seeing the group. If they know the name of the group, they can still send to it. There used to be some companies that provided a utility to moderate Notes groups but can't think of them right now.
Feedback response number WEBB7XBNS9 created by Peter Mullarky on 10/30/2009