Section 7.6.4 bullet point 2
"If a session bean instance is participating in a transaction, it is an error for a client to invoke a
method on the session object such that the transaction attribute in the deployment descriptor
would cause the container to execute the method in a different transaction context or in an
unspecified transaction context. In such a case, the container throws the java.rmi.RemoteException
to the client if the client is a remote client, or the javax.ejb.EJBException
if the client is a local client."
Or have I misunderstood the question?
Yes, thank you, this section answers my question..