Can I disable a specific member from having a sig?

<?php

//...

if ($profile_method == "input") {
if($userdata['userid'] == '123' ) {
// no input form for user xy
 } else {
   require_once INCLUDES."bbcode_include.php";
   echo "<tr>\n";
   echo "<td valign='top' class='tbl'>".$locale['uf_sig']."</td>\n";
   echo "<td class='tbl'><textarea name='user_sig' cols='60' rows='5' class='textbox' style='width:295px'>".(isset($user_data['user_sig']) ? $user_data['user_sig'] : "")."</textarea><br />\n";
   echo display_bbcodes("300px", "user_sig", "inputform", "smiley|b|i|u||center|small|url|mail|img|color")."</td>\n";
   echo "</tr>\n";
}
} elseif ($profile_method == "display") {
   // Not shown in profile
} elseif ($profile_method == "validate_insert") {
if($userdata['userid'] == '123' ) {
//no insert in db for user xy
 } else {
   $db_fields .= ", user_sig";
   $db_values .= ", '".(isset($_POST['user_sig']) ? stripinput(trim($_POST['user_sig'])) : "")."'";
}
} elseif ($profile_method == "validate_update") {
if($userdata['userid'] == '123' ) {
// no db update for user xy
 } else {
   $db_values .= ", user_sig='".(isset($_POST['user_sig']) ? stripinput(trim($_POST['user_sig'])) : "")."'";
}
}
?>