@Override
    public Element getSubsriptionErrorDetail() {
        return DocumentHelper.createElement(
                QName.get("closed-node", "http://jabber.org/protocol/pubsub#errors"));
    }
Only those on a whitelist may subscribe and retrieve items.

@author Matt Tucker
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/models/WhitelistAccess.java