http://www.npr.org/2017/08/01/540903038/u-s-citizen-held-by-...
https://www.aclu.org/other/constitution-100-mile-border-zone
ICE and CBP do conduct arrests pertaining to border violations within that 100 mile zone, but they aren't shaking down random passers-by for their iCloud passwords. They do have to follow due process.
I don't have citations because I can't prove a negative.
"In any event, even if the FBI had somehow 'hacked' into the SR Server in order to identify its IP address, such an investigative measure would not have run afoul of the Fourth Amendment," Turner wrote. "Because the SR Server was located outside the United States, the Fourth Amendment would not have required a warrant to search the server, whether for its IP address or otherwise."
https://arstechnica.com/tech-policy/2014/10/us-says-it-can-h...