In my last post (http://www.huffingtonpost.com/geoffrey-r-stone/is-the-nsas-bulk-telepho…), I described the evolution of Fourth Amendment doctrine to set the stage for analysis of the constitutionality of the NSA's bulk telephony meta-data program. As we saw, in thinking about the Fourth Amendment, the initial question turns on the meaning of the word "search."

To briefly review, a "search" historically was understood to be a physical intrusion into a physical space. The paradigm was a search of someone's home or briefcase. In the 1960s, the Supreme Court decided that, in light of modern methods of invading privacy, that definition was too narrow. It therefore re-defined a "search" for Fourth Amendment purposes as an effort by the government to obtain information about an individual that violates society's "reasonable expectations of privacy." Under this new definition, wiretapping, which had been held not to be a "search" under the traditional definition, was for the first time brought within the scope of the Fourth Amendment.

But that gave rise to a new question: How should "reasonable expectations of privacy" be defined? As a baseline, the Court assumed that methods of obtaining information that were known to the Framers and were not thought by the Framers to be "searches" should not be deemed "searches" under the new definition. Rather, the Court's primary concern was with new methods of invading privacy that, if left outside the scope of the Fourth Amendment, could dramatically shrink the degree of privacy that individuals had historically enjoyed.

Read more at The Huffington Post