I think this gets to the heart of how so much of this discussion misses the point. The question is not about solving CS problems. It's about determining the aut

I think this gets to the heart of how so much of this discussion misses the point. The question is not about solving CS problems. It's about determining the authenticity of the passenger's story. In this example, provided that the border agent is at least sufficiently aware that a BST question is a 'hard problem', the question may have simply been posed to observe if the passenger reacts appropriately to that. Even if the answer is "look, I've just been on a plane for 23 hours! you couldn't possibly expect me to..?", You're right, the agent couldn't. Tick! The response is consistent with the passenger's story. It's a bluff. Which is to stress a more important point: it's not for us to second guess the subtleties of a border agent's questioning. That's part of their professional training. -- That is of course, unless we have cause to believe the questioning is in some way unethical. And you raise (1), (2) and (3) that are clearly examples of unethical behaviour. But with respect to this story - where is the evidence that any of this happened? [1] This is _precisely_ why we should be careful not to generalize and be accurate in our criticism - if we are to be taken seriously in an area where there is understandably much cause for concern. [1]: To be clear: A technical question about a passenger's stated profession is not unethical. Yes, it would be unethical if the quality of the _technical_ answer was somehow tied to admittance. But again there's no evidence that that happened.