[davidw]

I don't know if this works or not, but this is what I have on one of the forums I am an admin at:

I did this to both postdata_presave and threadfpdata_presave hooklocations.

global $vbulletin;
		$pagetext =& $this->fetch_field('pagetext', 'post');
		if (($vbulletin->userinfo[posts] < 7) and (stristr($pagetext,'[url') or stristr($pagetext,'[URL') or stristr($pagetext,'[email') or stristr($pagetext,'[EMAIL') or stristr($pagetext,'www.') or stristr($pagetext,'mailto:') or stristr($pagetext,'http://'))) 
    {
     		//eval(standard_error(fetch_error('error_nourlallowed')));
				$this->error('error_nourlallowed');
				$return_value = false;
    }