No.  Being unmoderated is inherent to the group at the time
it was created. The closest that can be done is create a new
moderated group with a similar name and get the FAQ
maintainer to point the new people to it.

Every so often there's discussion of creating a moderated
soc.support.diet.low-carb.  It's never gotten off the ground.
There are for-pay moderation servers.  I pay the bill for one
such group and I am not willing to pay a second.  There is
free software but no one has stepped forward to supply a
free server to run it on.  There's a process to go through to
get a moderated newsgroup that I could do having gone
through the process before but without someone supplying
the free server it's not worth the effort.

There is a free software free server option available but it
is strictly robotic.  It's track record of catching spam
posts is about the same as the software most of us use
for our mailboxes.  Plenty of spam still gets through.  And
at best it can block trolls after their first posts - Consider
that a fair number of trolls are the ones who post a single
obnoxious cross-post as a part of some contest or attack
and then never come back.

The best that could be done with such posts is to
automatically reject any cross-posted message at all.  In
the case of cross-posts between diet support groups and
fat acceptance groups it's easy to class them all as trolls
without much loss of discussion, but it would also reject
all cross-posts to other diet support groups and to diabetes
support groups.  The price has a high potential for lost
traffic.

Also note there's a clear historical pattern whenever there
is a moderated/unmoderated pair of newsgroups in place -
Most folks stay on the unmoderated newsgroup because
most folks use killfiles so they don't see most of the bad
traffic.  The traffic on the mderated version stays forever
lower than the traffic on the unmoderated version and since
any one poster tends to not know UseNet history any one
poster tends to conclude that's a problem with the moderation
not a natural function of UseNet across topics.

Doug Freyburger
moderation team soc.religion.asatru, news.group.proposals
alternate moderator news.admin.moderation

You have to make a request in a special NG but I don't know which one.

Spammers are destroying this group.