This is an illegal search that violates the 4th amendment under
Kyllo v. United States, 533 U.S. 27 (2001)..
Originally Posted by The US Supreme Court
"Where, as here, the Government uses a device that is not in general public use, to explore details of a private home that would previously have been unknowable without physical intrusion, the surveillance is a Fourth Amendment “search,” and is presumptively unreasonable without a warrant."
Same should apply for a person as well for anything that's not in public view.
Not that TSA really cares what the law is that they're violating the 4th amendment, but it's good to see that there's precedent for smacking them down should anyone be harassed by this.