> our list has rules against flaming and we have a system of warning
> levels. [....]
 
Yow. You folks are a *lot* more patient than I'd be.
 
> poster has earned himself a public utimatum. he has since posted threats
> to complain to the site that houses the list (my employer) that we are
> violating his 1st amendment rights.
 
Rights to what? Freedom of the press belongs to those who own
presses. You are under no obligation to provide the facilities
for this yahoo to express himself. You are in no way impeding his
right to free expression if you refuse him the use of your
hardware.
 
> another poster has actually
> threatened to flood the email accounts of the administrators at my
> university to try and get the list shut down.
 
Let them try, and keep careful documentation of their actions.
This is certain evidence of harassment, and in some states, is
actionable. You should contact your system administrator and make
sure they're formally aware of what's going on at each step of
the way.
 
> i was wondering whether any other lists have had problems w/hostile
> posters who try to disrupt the list and cause great stress for other
> members of the list?
 
Yes. Usually a word to the administrators of the offending site
and copies of documentation of the offending messages and
complaints is sufficient to take care of the problem. I've only
had to block a site once, and they came around very quickly and
shut the bozo up when senior faculty and administration types
were affected.
 
> also, is there any protection for owners from this
> sort of harrassment?
 
There's not a lot of legal precedent in this area. Usually,
system administrators are reasonable people and try not to annoy
people too much.
 
 
> wednesday, thursday and friday posts. it looks like the problem may have
> stopped, but i've noticed that a lot of mailing sites are down (drycas
> and umkc for two), so its hard to tell.
> oh, i don't know if it matters, but our list is accessible through
> usenet as one of the bit.listserv lists. could this have something to do
> w/the problem?
 
You bet. This usually occurs when some Usenet site doesn't have
the duplicate article checking working right and decides to
resend bunches of articles back out with new message ids. It's
also pretty common with lists with large numbers of subscribers
that use some of the PD mail "systems" with gateways to the
Internet. If the gateways aren't properly configured, you
sometimes see this type of thing.
 
My opinion: tac nuke the twits and let them scream. If you've got
documentation of them being obnoxious, then you're covered.