The new airport screening measures involving millimeter wave technology and backscatter technology — together with the opt-out of a pat-down — have received a great deal of public attention. Back when the new measures were first widely introduced, I blogged about why a Fourth Amendment challenge to the new practices was an uphill battle. Today, the DC Circuit handed down an opinion in EPIC v. Department of Homeland Security holding that the new practices comply with the Fourth Amendment. I believe this is the first clear court ruling on the question, and it’s certainly the first from a federal court of appeals. The opinion is by Judge Douglas Ginsburg, and it was joined by Judges Henderson and Tatel. From the opinion:

[T]he petitioners argue that using [Advanced Imaging Technology] AIT for primary screening violates the Fourth Amendment because it is more invasive than is necessary to detect weapons or explosives. In view of the Supreme Court’s “repeated[] refus[al] to declare that only the least intrusive search practicable can be reasonable under the Fourth Amendment,” City of Ontario v. Quon, 130 S. Ct. 2619, 2632 (2010) (internal quotation marks omitted), and considering the measures taken by the TSA to safeguard personal privacy, we hold AIT screening does not violate the Fourth Amendment.

As other circuits have held, and as the Supreme Court has strongly suggested, screening passengers at an airport is an “administrative search” because the primary goal is not to determine whether any passenger has committed a crime but rather to protect the public from a terrorist attack. See United States v. Aukai, 497 F.3d 955, 958–63 (9th Cir. 2007) (en banc) (passenger search at airport checkpoint); United States v. Hartwell, 436 F.3d 174, 178–81 (3d Cir. 2006) (Alito, J.) (same); United States v. Edwards, 498 F.2d 496, 499–501 (2d Cir. 1974) (Friendly, J.) (carry-on baggage search at airport); see also Illinois v. Lidster, 540 U.S. 419 (2004) (police set up checkpoint to obtain information about earlier crash); Mich. Dep’t of State Police v. Sitz, 496 U.S. 444 (1990) (sobriety checkpoint). An administrative search does not require individualized suspicion. City of Indianapolis v. Edmond, 531 U.S. 32, 41, 47–48 (2000) (individualized suspicion required when police checkpoint is “primarily [for] general crime control,” that is, “to detect evidence of ordinary criminal wrongdoing” unlike “searches at places like airports … where the need for such measures to ensure public safety can be particularly acute”). Instead, whether an administrative search is “unreasonable” within the condemnation of the Fourth Amendment “is determined by assessing, on the one hand, the degree to which it intrudes upon an individual’s privacy and, on the other, the degree to which it is needed for the promotion of legitimate governmental interests.” United States v. Knights, 534 U.S. 112, 118-19 (2001) (internal quotation marks omitted).

That balance clearly favors the Government here. The need to search airline passengers “to ensure public safety can be particularly acute,” Edmond, 531 U.S. at 47–48, and, crucially, an AIT scanner, unlike a magnetometer, is capable of detecting, and therefore of deterring, attempts to carry aboard airplanes explosives in liquid or powder form. On the other side of the balance, we must acknowledge the steps the TSA has already taken to protect passenger privacy, in particular distorting the image created using AIT and deleting it as soon as the passenger has been cleared. More telling, any passenger may opt-out of AIT screening in favor of a patdown, which allows him to decide which of the two options for detecting a concealed, nonmetallic weapon or explosive is least invasive.

Contrary to the EPIC’s argument, it is not determinative that AIT is not the last step in a potentially escalating series of search techniques. In Hartwell, from which the petitioners tease out this argument, the Third Circuit upheld an airport search that started with a walk-through magnetometer, thence to scanning with a hand-held magnetometer and, when the TSA officer encountered a bulge in the passenger’s pocket, progressed (according to the passenger) to the officer’s removing a package of crack cocaine from that pocket. 436 F.3d at 175–76. The court noted, however, that its opinion, while describing the search at issue there as “minimally intrusive,” did “not purport to set the outer limits of intrusiveness in the airport context.” Id. at 180 & n.10. Nothing in Hartwell, that is, suggests the AIT scanners must be minimally intrusive to be consistent with the Fourth Amendment.