I'm thinking you could also just moderate the entire list for a few days
(with "Send= Editor,Hold,Confirm") and eventually he might get tired of
the fact that you won't approve his messages, no matter <where> they
come from...

The kicker is that with all of these freebie e-mail providers (HOTMAIL,
BIGFOOT, etc) he could jump to one of them from JUNO, making even freezing
all JUNO users out a waste of time.  And don't think he isn't that smart :)

You could also set

* Default-Options= REVIEW

in the list header and then it doesn't matter if he unsubs and resubs from
another address.  Legitimate subscribers could be set NOREVIEW later, after
a probation period.

Nathan