I've updated my post on the NSA data mining program. Is it legal? Well, it doesn't violate the Constitution. It's possible the telecom companies violated one or two statutes in turning the data over, but they have decent argument that one or more exceptions apply.
Whether the program is legal or not is an important question, although it may, in the end, be one on which reasonable and intelligent people differ. A question that we tend to ignore relates to the policy implications of this. On the one hand, we have people who privilege privacy. On the other, we have folks arguing for security.
Our notions of how privacy is best protected may need updating. Technology has affected things in two ways. On the security side, it is now possible for a relatively small group of people to do enormous damage. On the privacy side, we now have machines that can process enoromous amounts of information and identify patterns that may warrant further investigation all without any person ever looking at that data.
The first suggests the need for addtional vigilance. The second makes it possible. Yet our legal notions of how you protect privacy were developed in a simpler time. Even our statutory law seems to be modeled after a fourth amendment jurispridence that asks if something is a "search" or not. If it is, it can (generally) only be done if we have a particularized and individual determination that the specific communications to be monitored may be related to a crime, etc.
But now we have the ability to "monitor" communications in a less intrusive way. In both NSA programs, no person is listening to your calls or inspecting your call patterns. A computer is just processing generalized data about your calls, often in a way that each of us is subject to by private entities seeking to know our buying and credit habits. Our information won't be spit out unless it falls within some complicated mathematical logarithm. Maybe what we need is a definition of the circumstances under which that can happen and some type of judicial or independent review of the type of data mining that is permitted. Maybe we need limitations on how the results can be used withour further review. But if you read things like the FISA statute or these communications statutes, the drafters don't seem to have contemplated even the possibility of this type of thing.
That's one of the reasons that we can have this type of extended debate over whether something is legal or not. The statutes in question really weren't drafted with our world in mind.