The declassified and redacted opinion is here. I’m reading it now, and I hope to post some comments when I have finished. Meanwhile press coverage confirms my earlier suggestion that the problem was an overcollection problem. As the Post summarizes:
Under the program, the NSA for three years diverted large volumes of international data passing through fiber-optic cables in the United States into a repository where the material could be stored temporarily for processing and for the selection of foreign communications, rather than domestic ones. But in practice, the NSA was unable to filter out the communications between Americans.
According to NSA estimates, the agency may have been collecting as many as 56,000 “wholly domestic” communications each year.
As I have said before, it’s all about the filters. More when I have had a chance to read the full opinion.