The ACLU thinks the new airport searches are both unreasonable and unconstitutional for primary screening for at least five reasons:

In the past, courts have said that airport screening is constitutional so long as it is "reasonable"--and searches are reasonable if they are minimally intrusive given the threat they are designed to prevent, and are well tailored to protect privacy.

Remember the Fourth Amendment? It is supposed to protect you from unreasonable searches and seizures. It is the source of our expectation of privacy, and the notion that law-abiding people have a right to be left alone.

As we end the year with another period of hectic holiday travel, one thing that is being subjected to more indignities at the airport than our scanned and groped bodies is the US Constitution.

First, the scanners are unreasonable because they are not effective at keeping harmful material off planes. A Government Accountability Office report says it "remains unclear" whether the machines would have detected three ounces of the chemical powder PETN carried by "underwear bomber" Umar Farouk Abdulmutallab--whose attempt to blow up a plane in 2009 was the impetus for the push for scanners. Furthermore, they find it hard to deal with folds in clothing and the body, and do not detect anything carried in body cavities.



The standard "full body" patdown--in which the genitals are surrounded but not directly touched (that is left for the "resolution" patdown, which can be done when agents feel there is a need to investigate further)--would probably also have failed to detect the underwear bomber's explosives or anything carried in a body cavity.

Second, they are unreasonable because they might make screening even less effective than it was under the old system. Why? They are due to replace metal detectors--which are not dependent on human observation. Both whole body scanners and full body patdowns are totally dependent on the person doing the screening, and we know there is a huge problem of operator inattention as the hours go by.

Third, they are unreasonable because both the machines and the patdowns have unknown health and public safety consequences. We simply don't know the health risks because no independent studies have been done. But serious concerns have been expressed in a letter from eminent biochemists and cancer experts from the University of California. They say there could be long-term consequences for older travelers, children, pregnant women, people who have had radiation therapy, and for the testicles of male travelers.

Then there are the psychological consequences of both scanners and patdowns. The more than one thousand complaints received by the ACLU reveal widespread feelings of humiliation, including from breast cancer survivors, transgender people, people wearing colostomy bags, people in wheelchairs, and people for whom personal modesty is a religious requirement.

For those concerned about modesty, TSA of course says the images will not be retained and certainly not shared. But they had originally said the images could not be retained and stored, but had to backtrack after a document obtained through a Freedom of Information Act lawsuit proved that was factually wrong.

The aggressive patdowns of small children who have been taught not to let strangers touch them is another serious issue. Ken Wooden, the founder of Child Lures Protection, recently warned that the TSA's recommendation that children be told the patdown is a "game" could potentially be putting children in danger because it will make them more willing to cooperate with sex predators.

Fourth, they are unreasonable because there are other approaches to airline safety that would not have the same privacy consequences. There are, for instance, machines being tested in Amsterdam's Schipol airport that show the human body as a stick figure and detect "anomalies." There are still potential health problems, but these scanning devices are not invasive in the same degree as those installed at US airports.

There is other technology that would be both safer and more protective of privacy. Why not use some of the $2 billion being spent on scanners to perfect the "puffer" machines that detect explosive material with a puff of air for a fraction of the cost of scanning machines?

Better yet, why not target actual suspects and not the entire traveling public? The underwear bomber should have been stopped before getting on a plane in the first place, as he was on a UK watch list, his father had told the US Embassy and CIA officials about his son's possible ties to extremists, and his name had been deposited in the National Counterterrorism Center's database. Our intelligence agencies, which cost taxpayers $60 billion annually, dropped the ball when they let him get on a plane. Why make all airline passengers pay for their mistakes?

Fifth and finally, subjecting the traveling public to such an invasive search policy without any suspicion of wrongdoing essentially asks us to trade the liberty guaranteed us by the Constitution for what the security expert Bruce Schneier has called "security theater"--something which makes people feel that safety issues are being addressed while doing little to enhance actual security. Schneier says only two things have really made airplanes appreciably safer from terrorist attacks--strengthening and locking cockpit doors, and training passengers to resist terrorist attacks.

Would you rather the TSA subject kids to aggressive patdowns or focus on screening airline cargo and figuring out how to keep electronic flight controls and navigation systems safe from electromagnetic or cyberattack? Would you rather spend millions on equipping airports with full body scanners or on the overhaul of our aging aircraft? While there have been several crashes of planes since 2001 because of equipment failure, not a single plane has brought down by terrorists.

While the security industry has ballooned, our constitutional liberties and protections have shrunk. We have to get our priorities right. We all want air travel to be safe. Our best line of defense is using evidence-based, targeted investigations to stop plotters before they get to an airport.

If there is individualized suspicion--a good reason--to subject a particular passenger to an enhanced patdown or scan, then it is appropriate to undertake such a search. But they should not be used for primary screening purposes.