Do you have a WELCOME/Netiquette file? If so and "they" post contrary to your charter, then do what any responsible list-owner would do: either communicate directly with said offenders, SET them to either REVIEW or NOPOST, UNSUBSRIBE them, or finally filter= them. If OTOH you know that they are rogue, simply boot them. They will be known by what they do post (if you don't boot them). /P