Well, you can certainly "shoot first" (delete+filter) and "ask
questions later."    There are intermediate steps too, depending
on the exact nature of the bounce back to the list: is the
bounce really coming FROM the subscriber's e-mail address?  if
not, maybe your list definitions are setup to encourage SPAM
and other non-subscriber distributions.
 
The user could be inhibited by "simple" list-owner command
so that their contributions are either bounced or sent to
the moderator (SET listname NOPOST | REVIEW FOR luser@node).
 
Reducing the frequency is sometimes effective (SET DIGEST | INDEX).
 
List Policies are as diverse as the list-owners.
 
/Pete Weiss