I disagree 100%, anyone who is traveling with an emergency passport will be subject to further review. As someone who worked for the airlines it is not unusual for anyone who does not present the same documents you left the USA with to be questioned. Again, you are giving way too much credit to CBP by thinking that his "being detained" had anything to do with the incident in the DR. I am sure when he and his father left the US Embassy, they were under the impression that the travel documents were fine. If you travel frequently then you are aware that on any given day you can be detained for the smallest thing, just depends on the agent and how they are feeling that day. Not sure what the purpose is for the link you posted from the Univ of Pitt, but nice to know.