Accessing published items to a node is expecting that requester is subscribed to the node

" * If the access model is "open", the service SHOULD allow any entity (whether or not it is subscribed) to retrieve items.

• If the access model is "presence", the service SHOULD allow any entity that is subscribed to the owner's presence to retrieve items.

• If the access model is "roster", the service SHOULD allow any entity that is subscribed to the owner's presence and contained in the relevant roster group(s) to retrieve items.

• If the access model is "authorize" or "whitelist", the service MUST allow only subscribed entities to retrieve items.
  "

"If the requesting entity has multiple subscriptions to the node but does not specify a subscription ID, the service MUST return a <bad-request/> error to the subscriber, which SHOULD also contain a pubsub-specific error condition of <subid-required/>."

The pubsub service should only validate that a subID was provided and that the subID is valid when the requester is subscribed to the node. If the requester is not subscribed and the access model allowed the requester to retrieved the items then do not check the subID attribute.