A question for Real Lawyers on the circuit split on the border search exception for digital device searches (https://www.findlaw.com/legalblogs/law-and-life/cbp-border-phone-searches-face-patchwork-of-rules-for-returning-u-s-citizens/): what circuit’s rules control what can be done in a border search outside the physical boundaries of the country, e.g., at a Canadian airport?
CBP Border Phone Searches Face Patchwork of Rules for Returning U.S. Citizens - FindLaw

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@SteveBellovin Why such a complicated question at such an early hour?

I certainly do not know the answer, but a few thoughts did pop into my still groggy head...

First is precisely where did the search happen? For instance was it in one of those US immigration/customs stations that are physically at Canadian airports? Are those under any sort of treaty arrangement?

Second, if I remember correctly, didn't SCOTUS rule on the geographic extent of district court orders (i.e. to block orders that cover outside of the court's geographic bailiwick.)

Third is that we always seem to assume that phone searches are looking for data. I can imagine that when one is looking for explosives or drugs that a search could be to weigh the phone. And for data, what about cloud data (wherever that is) that is not on the phone and for which the phone is merely a portal?

@karlauerbach The agreement is at https://www.treaty-accord.gc.ca/text-texte.aspx?id=105453, but as best I can tell is not a "treaty" under US law.
View Treaty - Canada.ca