Something

alias blacklist {
  /set %bl [ $+ [ $nick ] ] 1
  /echo -a $nick has been blacklisted
  if ($nick !isreg $chan) {
    /mode $chan +b $address($nick,2)
    /kick $chan $nick
  }
}
on *:JOIN:#: {
  if (%bl [ $+ [ $nick ] ] == 1 && $me !isreg $chan) {
    /mode $chan +b $address($nick,2)
    /kick $chan $nick
  }
}