Still, that does not answer the policy question the law cannot answer: Even assuming the government is permitted to collect this data, why does it need to do so – how does collecting massive amounts of innocent people’s communications information make us safer?

Furthermore, even the legal argument is on thin ice once you accept the premise that the “expectation of privacy” standard provides A with some inchoate Fourth Amendment interest in B’s property (where B is a private company keeping records of A’s activity). After all, the traditional Fourth Amendment logic is that government must develop evidence that gives rise to reasonable, particularized suspicion of wrongdoing before it may seize property. The NSA procedure, to the contrary, allows government to seize first and develop evidence later – with the proviso that there will be no search of what has been seized in the meantime. If we concede for argument’s sake that there is a liberty interest here, government seizure without individualized suspicion is not how the Constitution normally works.

Exceptions have been made for “special needs” – searches and seizures that are permitted without individualized suspicion in cases where government can show a compelling need other than gathering evidence for prosecution (e.g., drug testing in public schools). But that gets us straight back to the question: why do we need to do this? It remains unanswered in the minds of many people – very much including many conservatives who care deeply about national security but do not want to be snookered into ceding the government powers that have a very high potential for abuse with an apparently low – or even non-existent – return on security. Quite reasonably these conservatives ask: Why can’t you do what government has always done: develop evidence rising to reasonable suspicion or probable cause first, and then seize the data with court authorization?

I do not mean to suggest that there has been no effort to answer the why question. General Keith Alexander, the NSA chief for whom high esteem cuts across party and ideological lines, says that the program has been material to the prevention of several terrorist attacks. More concrete arguments have been made by Stewart Baker and Jim Carafano, who are extremely knowledgeable about how giant data collections can be mined in order, with minimal intrusion on the privacy of non-suspected persons, to detect unique terrorist communications patterns. The innocent communications are needed, they suggest, in order to make the guilty communications stand out.

General Alexander puts that contention this way: “You need the haystack to find the needle.” I confess to finding this analogy maddening. The hay is what makes the needle much harder to find; it doesn’t help people understand why collecting an ocean of data is useful to locating a few droplets of jihad. And I say that as a supporter of the NSA program who is convinced that its potential intrusion on my privacy is so trivial that if it can help stop another 9/11, it is well worth doing. But the president – the guy with the bully pulpit who purportedly believes the program is essential – is AWOL in this debate because his left-wing base is opposed to national security measures. So the burden of persuasion falls on the NSA chief. If his needle-in-the-haystack argument doesn’t move me, how is it possibly going to move people who are far more skeptical?

If there is a more convincing case to be made on the why question – why collecting huge amounts of data pertinent to innocent people is essential to detecting terrorist communication patterns – it must be made pronto. Again, reluctance on the part of knowledgeable people to say more than they have for fear of educating our enemies is perfectly understandable, even admirable. But national-security conservatives have to face facts: We are gradually losing this debate. Being right on the adequacy of the NSA programs’ structural safeguards, and being right on the law, will count for nothing if Americans are not convinced – quickly – that there is a real, material, comprehensible connection between the massive data collection and the prevention of terrorist attacks.

(Thumbnail on PJM homepage based on a modified image.)