The problem is, it doesn't violate the constitution. I'll give a brief rundown of some of the problems of challenging the constitutionality of TSA. I'm breaking my rule of no more than 1/10th of an hour (6 minutes is a standard billing unit), but I'm only saying it once. I will not respond to any post even good questions since every time I say what the state of the law is people act like I am personally responsible for the American legal system. They think I and the law are one in the same. We aren't.
I will cover three major issues. Consent doctrine, improper method, and fundamental right.
Consent:
You have consented to be searched including a pat down. You have waived your 4th Amendment rights in this specific situation, specific time, and specific manner. Consent must be given voluntarily, knowingly, and intelligently. Voluntarily means you bought your ticket of your own free will, or in other words, you voluntarily put yourself in the position to be searched. Private actors, your employer, don't have to meet this standard because they don't have to follow the 4th Amendment. Knowingly and intelligently just means you recognize that you may be searched and know what the search may entail. These are all the disclaimers that you click check boxes for or sign off on. It must be noted that an argument that you didn't realize just how invasive it would be is a improper method argument not consent.
Your main problem with attacking consent is that you cannot attack it in a vacuum. That is, attack consent in relation to TSA and you attack all consent laws based upon the voluntary, knowingly, and intelligently standard. There is no TSA specific consent doctrine. You have two ways to do this. First, attack the consent doctrine itself. Basically, make an argument that constitutional rights cannot be waived. Say that even if done voluntarily, knowingly, and intelligently rights cannot be waived. This argument has no chance. However, if it sounds good then contact your representative to pass an amendment. At first blush it sounds good, but I'd like to know more about the overall ramifications before pushing it.
Your second line of attack is arguing that purchasing a ticket and arriving at the airport does not meet the proper standard. Better than the first option, but still a tough row to hoe. The voluntarily, knowingly, and intelligently standard is objective. That means the court looks at affirmative steps that constitute consent. Knowing you may be searched you search for a ticket, buy a ticket, register an account, input credit card information, click check boxes affirming you know about the possibility of search, you ultimately buy your ticket, arrive at the airport, check in with the airlines, and then head to the security check point. These are all affirmative steps. At any point you could have revoked. Compare with a Miranda waiver. Police put a piece of paper in front of you, you read it, then sign. You must differentiate the affirmative steps for the Miranda waiver with buying a ticket. I don't see how this can be done. There is much more pressure to comply in front of police than in front of your computer.
Bottom line, separating consent doctrine as it applies to TSA from other law enforcement or government agencies is almost impossible, and invalidating global consent doctrine is a non-starter.
However, just because you have consented to a search does not mean it can be performed in any manner. It must be done in a proper method.
Improper method:
This issue relates to the claims that TSA searches are "groping," "sexual molestation," or any other criminal charge. First, TSA agents do not have government immunity from these charges. Since they are outside the framework of their job they cannot be immunized. Second, proper TSA pat downs are not criminal acts. TSA pat downs are modeled after other government agency or law enforcement pat downs (the AIT and backscatter machines follow similar issues. Though the backscatter, if proven harmful, would be moved to its own issue separate from the other searches). Specifically, the standard pat down is similar to what parole officers administer to juvenile offenders, and the resolution pat down is similar to a police pat down. That means, again, you have two methods of attack. First, claim all pat down searches are criminal. Second, that TSA pat downs are different from all other agency or law enforcement searches.
Your first type of argument would fail just like the global consent argument. You're attacking too big a piece of criminal law. If police can't pat a suspect down then what can they do? A quick side note, police need either consent, reasonable suspicion (certain cases only), or probable cause to search. As stated above, TSA searches fall under consent. I don't see any way a court would make police searches illegal.
Your second type of argument is better but still flat. TSA searches aren't new. They are based upon other agency and law enforcement searches. You would have to differentiate other agency and law enforcement searches from TSA searches. Those claiming TSA searches to be molestation or any other criminal charge that would be your difference. Basically, you would say police searches are OK because the standard procedure does not molest the suspect. TSA searches are improper because the TSA standard procedure is molestation. This claim is irrespective to individual and is a global claim. As stated above, individuals that do improper pat downs, outside of TSA procedures, are ripe for criminal charges. But getting an individual wouldn't invalidate TSA unless you can prove that the person's actions were in line with TSA procedures. Further, even if you win on this count it just means the agency can adjust its procedures. However, a scandal like this and TSA would just be eliminated.
Improper method is probably a better argument then consent, but you still have a problem with the parallels with other agency and law enforcement. Are TSA searches really that different from other searches? From what I gather from law enforcement friends they aren't. If I were suing TSA I would definitely look into this. I'd get the official operation procedures but then research actual procedures. The standard de jure vs. de facto implementation. I don't have to prove that the regulations specifically violate improper method; I just have to prove that the official implementation does. You still have the sticking point of showing that even if the de facto implementation violates it's still different than de facto implementation that has been held constitutional on the law enforcement side. Again, you aren't attacking TSA alone.
Fundamental right:
Flying is not a fundamental right. Your ability to travel is a fundamental right as stated in Heart of Atlanta Motel. But that case didn't hold that your preferred or more efficient method of travel was a fundamental right. I would attack here. Justice Scalia in the thermal imaging case (holding police use of thermal imaging cameras to find pot growers an illegal search) put dicta in basically saying he would adjust the law as technology improves. In that case he said if thermal imaging became ubiquitous it may no longer be an illegal search. That would be my parallel. That is, airline travel in the last few decades has become ubiquitous in a increasingly global world. US Citizens no longer are satisfied to stay in the US. The fundamental right to the ability to travel must include the ability to travel outside of the US. Couple that with increasingly limited vacation time resulting in really no way to travel by car then boat to participate in such international travel then air travel must be fundamental. Because air travel is fundamental then TSA searches must pass strict scrutiny and be the least invasive and least discriminatory alternative. That is, TSA can only implement procedures that are absolutely necessary to achieve their goal. Most of TSA wouldn't meet this standard. Almost nothing ever does. The Korematsu (WWII concentration camps) did, but that's because the court deferred to the military. That case wouldn't pass today.
The problem with this is 1) differentiating air travel with all other modes of travel and 2) all the other laws and regulations implicated by this decision. First, you'd have a hard time getting all modes of travel to be fundamental. Every law regulating or licensing would immediately come under fire. And meeting strict scrutiny is hard. It would cause chaos in transportation law. Second, other laws implicated like passports, customs, and other rules would have to sustain a strict scrutiny attack. I think 1 actually wouldn't be too hard. In today's world air travel really is the de facto option for some destinations. I wouldn't have people that want to fly from LA to Las Vegas as plaintiffs, but I would if they refused to go to Australia or Africa because of TSA and an impracticability to drive then boat. The argument isn't that air travel is more efficient, the court won't care, but that air travel is the only de facto option to get there. I think the government would push number 2 really hard, but I doubt the court would care too much about that.
The fundamental right is probably your best bet, and it would change TSA over night. Pat downs would be gone and all that would be left would be x-ray scanners, document checkers, then the AIT for passengers that continually set off the scanners. Everyone else just goes through. I doubt they would even allow random screening.
I've whittled things down to basics, but that's what your facing. You cannot challenge TSAs constitutionality without facing a lot of other areas. You can't attack in a bubble unless you can differentiate TSA from other agencies and law enforcement. So you're going after global consent doctrine not just consent to TSA. You are attacking the method of pat down searches of all government agencies and law enforcement not just TSA.
I know, people will attack me as being a "dictatorship apologist" and being a yah! rah! TSA fan, but I'm not. I want TSA to go away too, but I can't go into court and yell it's unconstitutional because I say so or because slashdot says so. You can't ignore Supreme Court precedent just because you don't like it or don't know about it. Ever since Marbury v. Madison was decided the Supreme Court has been the arbiter of constitutionality. In the court system you have to work within their framework just like this appellate court did. What you need to realize is that claiming TSA is unconstitutional is not as easy as saying "read the Fourth Amendment." You must consider Supreme Court interpretation as well.