Stewart Baker: Why The NSA Needs Your Phone Calls

I wondered below what the rationale could be for PRISM.  Baker, at FP, makes some good points:

Let's start with the order. It seems to come from the court established to oversee intelligence gathering that touches the United States. Right off the bat, that means that this is not some warrantless or extrastatutory surveillance program. The government had to convince up to a dozen life-tenured members of the federal judiciary that the order was lawful. You may not like the legal interpretation that produced this order, but you can't say it's lawless.
In fact, it's a near certainty that the legal theory behind orders of this sort has been carefully examined by all three branches of the government and by both political parties. 

 And:

Ah, you say, but the scandal here isn't what has been done illegally -- it's what has been done legally. Even if it's lawful, how can the government justify spying on every American's phone calls?

It can't. No one has repealed the laws that prohibit the National Security Agency (NSA) from targeting Americans unless it has probable cause to believe that they are spies or terrorists. So under the law, the NSA remains prohibited from collecting information on Americans.

On top of that, national security law also requires that the government "minimize" its collection and use of information about Americans -- a requirement that has spawned elaborate rules that strictly limit what the agency can do with information it has already collected. Thus, one effect of "post-collection minimization" is that the NSA may find itself prohibited from looking at or using data that it has lawfully collected.

 And this "minimization," Baker claims, is key. The NSA might need to collect a lot of data, but there are rules about what data it can and can't use.

But why collect all that? Here's the speculation/hypothesis: even "decent improvised tradecraft" might very well involve terrorists using multiple cell phones from multiple carriers. To be able to track the calls, the NSA would have to grab a bunch of data when it needed it, and figure out what it's legal to use later.

The whole thing is worth a read.

It seems a little unlikely to me that all three branches of government have gone insane. So I'm willing to suspend my outrage for a bit until we hear what they have to say.