I remember an instance on HN maybe 9 years ago or so where the treasurer of a third-party on the US was detained at the airport and questioned about the amount

I remember an instance on HN maybe 9 years ago or so where the treasurer of a third-party on the US was detained at the airport and questioned about the amount of cash he was carrying. Probably seems reasonable, as I would imagine most people carrying massive quantities of cash aren't up to any good. But no one was able to tell him if he was actually required to answer the questions in order to be allowed to travel and retain ownership of the cash. He kept getting passed around until eventually someone told him that yes, he was required to answer the question. Which I believe is incorrect - I expect they got sued afterward. edit: I believe this was the incident: https://www.aclu.org/press-releases/aclu-sues-dhs-over-unlawful-tsa-searches-and-detention https://www.aclu.org/press-releases/aclu-sues-dhs-over-unlaw... edit 2: It was $4700. Wouldn't raise eyebrows in a bank withdrawal. Not what I had in mind when I said "massive".