You may have noticed that Amtrak shows up at the lower left in the diagram above. Amtrak sends API data for passengers on its few international trains (to and from Canada) to CBP. But as of now, so far as we can tell from CBP’s responses to requests for travel records and Amtrak’s (still incomplete) responses to our Freedom Of Information Act requests, Amtrak’s data-sharing with CBP is still (1) limited to passengers on international trains, and (2) a one-way feed of passenger surveillance information, not an interactive permission system. So far as we can tell, Amtrak hasn’t yet installed anything comparable to the BPPR control lines that give CBP and TSA the ability to exercise prior restraint of air travel. https://papersplease.org/wp/2021/01/19/put-them-on-the-no-fly-list/