They invented a device that can discern the US-Citizenship-status of anyone merely by knowing the phone's local usage details and privacy-respecting information about the data transmitted.
Well, not really, but that's what would be necessary for such a claim to hold any water.
Why would that be necessary? If they are targeting an individual for investigation at this level certainly they have already determined their citizenship status well in advance. From there obtaining permission to investigate citizens who are in contact with this individual probably isn't too difficult. I guess I just don't see why it would have to be some magical automated system when it can be handled on a case-by-case basis quite easily.
Well, not really, but that's what would be necessary for such a claim to hold any water.