The somber reality is US CBP exercises athority to do this anywhere within 100 miles of the border: https://www.aclu.org/other/constitution-100-mile-border-zone
And now an annoying aside. I really wish the ACLU was sincere in fighting this but they won't get any more of my money. I used to support the ACLU because these were the types of P1 issues they would battle. It seems in the last years it's faded to more social justice platform. Fine for them if that's what they believe are the most pressing issues of our time, but not my P1 constitutional concerns.
What's the point of anything if the government can railroad your 1st and 4th amendment rights? Are there good alternatives to the ACLU of yore?