[Adrian Schneider]

You could add something like

PHP Code:

if ($bbuserinfo[usergroupid] == X)
{
    $errormessage = "Custom Error Message";
    eval('print_output("' . fetch_template('STANDARD_ERROR') . '");');
} 


Or if there are multiple, you could use in_member_of($bbuserinfo, X,Y,Z)

Originally Posted by Paul M

This is already a usergroup permission ;

General Permissions > Can View Member Info = Yes or No

Your method is probably easier.