WesternInfidels

Legal Information Institute, Searches at International Borders suggests that the Supreme Court decided “searches made at the border … are reasonable simply by virtue of the fact that they occur at the border” in 1977.

This has always been a well known rule.

Smartphones and the rules surrounding them at border searches are still pretty new, and they’re likely enough to change. I think you might be overestimating the well-known-ness of these customs.