Re: The Motivation For Face Scanning Is (Presumably)...
to recognize wanted criminals,
Considering the TSA has consistently failed utterly to do this, even when hiring its own employees, I don't have much hope the CBP will do better.
people on a no-fly list,
The no-fly list is pointless security theater, and everyone knows it. (Also, it applies to the TSA, not the CBP, and it's the latter who are deploying the facial-recognition tech.) The TSA would prefer not to identify people on the no-fly list, because preventing them from flying doesn't do shit to improve security, and it's a hassle for everyone involved, including other people trying to get through security. The list is just for the TSA to use as (bogus) evidence that they're accomplishing something.
or potential terrorists
Who isn't a potential terrorist? What attribute prevents someone from ever becoming a terrorist? Well, being dead, I guess. But aside from that?
What you want to be able to detect is actual terrorists. Given the small number of actual terrorists in the world population, and the presumably much smaller fraction of those for whom we have decent facial photographs, automated detection is going to perform very badly. An automated system would have to have astounding precision and recall to provide decent false-positive and false-negative rates given the very low rate of true occurrence in the data.
Of course, it's also possible someone at the DHS misunderstood Miss Pym Disposes and is hoping to reinvent criminal physiognomy. "Yes, sir, the AI positively identified this man as a terrorist based on his eyebrow shape."