Once again the classloader used to resollve the load under JAXBContext.newInstance was the war classloader. I worked round this by adding 'com.sun.xml.bind services export' to the dependencies in the war manifest.mf. However, I think it would be better if the modules which import it (both jaxws-client and jbossws-cxf-client) also exported it. It might be good if all the dependencies weer scrutinised to see whether they need re-exporting.
https://issues.jboss.org/browse/JBWS-3309