I assume it has to do with a federal law that grants immigration agents broad searches and inspections and technically the Fourth Amendment does not fully apply as long as they are within 100 miles of the border or in the functional equivalent of a border (like an airport). The ACLU has a summary page about this.[1]

[1]: https://www.aclu.org/documents/constitution-100-mile-border-...

I wouldn't think that would extend to threats like a cavity search and flagging their passport.

Lady named Cervantes had doctors warrantlessly finger raping her and lost due to jurisdiction fuck fuck games ( i also talked to her lawyer). Happen all the time, CBP lost once iirc in new mexico and letters were sent and thenn promptly ignored. CBP bragged to me about it. They also bragged about flagging trans people claiming their surgical dong was drugs and sending them for exam to fuck with them.

It's not just about security, they admitted they fuck with innocent people just for enjoyment. They cannot be stopped as the courts don't really see them as beholden to the Constitution, it's a huge legal hole and the officers have a crystal clear understanding of this.

This is also why when they needed an unbeholden army to send to Portland to pick up protesters in unmarked vans, they used CBP.

https://holdcbpaccountable.org/2016/08/09/cervantes-v-united...

"We've tried litigating these cases before and after always failing we gave up pursuing these kinds of cases" -- in so many words.