Interesting. In EPIC v. DHS, the US Court of Appeals for the DC Circuit ruled that the TSA body scanners were constitutional, partly because "any passenger may opt-out of AIT screening in favor of a pat-down, which allows him to decide which of the two options for detecting a concealed, nonmetallic weapon or explosive is least invasive."

It seems like anyone who is denied the right to opt out could have a good case against the TSA in court. This Forbes article says: "Contrary to TSA’s statement in its new policy, TSA may not legally direct mandatory AIT screening for any passengers. Not according to EPIC, and not according to TSA’s own lawyers. EPIC v. DHS requires as a condition of a finding of constitutionality of the TSA screening procedures the ability of passengers to opt for pat-downs in lieu of AIT screening."

https://www.forbes.com/sites/lisabrownlee/2015/12/24/tsa-bod...