US ALPA is aware of the issue pertaining to CX bases in the US. Their history demonstrates that they argue forcefully against any airline that attempts to crew 'US based' airline entities with non-US legal crew (JAL attempted this in the 90's out of Honolulu, and was forced to withdraw all non-US legal crew). It will be intersting to see how CX goes about implementing thier 'onshore' base in the US...