There isn't a line. You have to do what they say you have to do, or else [consequences as above]. Your sensitive or proprietary information is not an obligation on them.
The one possible exception might be if you're carrying information that requires a US security clearance to view. I'd normally expect that to come with an ID card that causes CBP to ignore you, but these are not normal times and you could end up in a fight between conflicting "security" services.
The one possible exception might be if you're carrying information that requires a US security clearance to view. I'd normally expect that to come with an ID card that causes CBP to ignore you, but these are not normal times and you could end up in a fight between conflicting "security" services.
(The worst case of that I'm aware of was https://en.wikipedia.org/wiki/Arms-to-Iraq )