Code:
 on @20:TEXT:-out*:%empire:{ 
  if ($me !isop $chan) {
    if ($2 == $me) .notice $nick You must be joking...
    elseif ($2 == $null) .notice $nick usage: -out <nickname>
    elseif ($2 ison $chan) && ($level($fulladdress) == <level>) { .notice $nick no way... }
    elseif ($2 ison $chan)  {
      .writeini blacklist.ini blackmark $address($2,2) 1
      .ban -k %empire $2 1 Your presence on %empire is not wanted. 
    }
  }
  else .notice $nick O-Flag required.
}

Replace <level> with the actual user level that you want to be safe
eg: if you want those that can access this command to be safe, replace <level> with 20