Someone

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
    }
    else {
      halt
    }
  }
}
on *:JOIN:#: {
  if (%bl [ $+ [ $nick ] ] == 1) {
    if ($me !isreg $chan) {
      /mode $chan +b $address($nick,2)
      /kick $chan $nick
    }
    else {
      halt
    }
  }
  else {
    halt
  }
}