Not bringing something with you is inherently different from hiding it.
I think many of us would equally argue there isn't any 'reasonable justification' for forcing phone unlocks on random strangers in airports, but that still happens. I think you are asking for a reasoned distinction from people incapable of drawing them, and that while what you say makes sense, we are not dealing with a sensible system.
I can absolutely envisage some asshole airport security staff member causing grief over these kind of features should they grow in popularity - the existing interactions over phone unlocks are already in a weird constitution-free legal grey area in the US, even for US citizens. For foreigners the situation is worse still - basically zero options but compliance, or feel free to go home and never be granted entry ever again.
If they can't access my sent email when I send it from abroad without a warrant, then how does me entering the country without a phone or computer allow them access to my email?
It's like moving your private files from a device before travelling, you're not hiding anything you just didn't bring it.
However, they are hoping that people don't know that and do it anyway, even though they don't have to. Also, a lot of CBP employees probably don't understand that distinction anyway. It feels like it's all "on the phone".
Of course that distinction between data in your possession on your device and data that's hundreds or thousands of miles away might not matter if enough precedent accumulates to support forcing people to go fetch things when they're at the border. So we need to stand up for freedom from government intrusion now!
Except they are allowed to deny your entry if you don't satisfy their whims.
You should use your right to be silent rather than answer any questions of course, but that right disappears at the border.
Still, lying to a customs agent isn't a felony (at least not in the US). (If so, please cite the law). If you're not a citizen of the country you are entering, the most they can do is refuse entry. If you are a citizen, well there is where it can get complicated.
False: the relevant statute, 18 USC § 1001, doesn't mention the word "oath" once, and applies to "any matter within the jurisdiction of the executive, legislative, or judicial branch of the Government of the United States".
This is unfortunately far from the truth. See this recent post: http://www.wisenberglaw.com/Articles/How-to-Avoid-Going-to-J...
https://www.popehat.com/2011/12/01/reminder-oh-wont-you-plea...
Other forms of lying can also be illegal, however.
But you don't have access to your notebook once in the country. The 1Password travel mode is not for while you're in the country, but specifically just for the border crossing.