/msg $C UNREGISTER <#channel> [<confirmation>]
Unregisters a channel that is registered with $b$C$b. $bIMPORTANT$b: Once the channel is unregistered, the userlist $bcannot$b be recovered.
If you are not network staff, you must add a confimation string to the end of your line to confirm the unregistration.  If you leave it out, $C will show the proper confirmation string.
$uSee Also:$u register