In a 68-page opinion, Federal District Judge Richard J. Leon of the District of Columbia ruled yesterday in Klayman v. Obama that the NSA's systematic collection of telephone metadata of millions of citizens violates the Fourth Amendment's prohibition on unreasonable searches.  

The opinion highlights an important issue that will have implications beyond the constitutional dispute in that case -- how expectations of privacy are evolving in light of changing technologies and the rapidly expanding use of the internet and mobile phones.    

Judge Leon's ruling concerns the government's collection of "metadata" about telephone calls, such as information about what numbers were called, when calls were made, and how long they lasted.  The government maintains that, under the program at issue, the NSA were not storing information about the content of calls or the participants' names, addresses or financial information.   

Relying on the United States Supreme Court opinion in Smith v. Maryland, government lawyers argued that individuals have no expectation of privacy, let alone a reasonable one, with respect to telephone service provider metadata.  Smith involved an investigation into threatening and obscene phone calls that a robbery victim had received.  Without obtaining a warrant or court order, the police installed a "pen register" to record numbers dialed from a telephone at Smith's home.

The Supreme Court ruled that Smith had no reasonable expectation of privacy in the numbers dialed, since he voluntarily submitted this information to the phone company and reasonably should have known that the company maintained this information as business records.  

Leon did not find the government's precedent compelling.  As the judge phrased the issue,

When do present-day circumstances -- the evolutions in the Government's surveillance capabilities, citizen's phone habits, and the relationship between the NSA and telecom companies -- become so thoroughly unlike those considered by the Supreme Court thirty-four years ago that a precedent like Smith simply does not apply?"  

For Leon, that time had come. He found Smith distinguishable; the case involved the collection of limited telephone data for a few weeks. Klayman on the other hand concerns the creation and maintenance of a historical database containing information about calls made by everyone in the country.    

The government's ability to store, collect, and analyze phone data not only is much greater now than in 1979, but the amount and type of available metadata are much greater as well. As the judge noted,

[data that] once would have revealed a few scattered lines of information about a person now reveal an entire mosaic -- a vibrant and constantly updating picture of the person's life." 

Some would argue that changes in technology and the ubiquitous storing and analysis of metadata by companies and the government would lower individual expectations of privacy.  Taking the opposite view, Judge Leon assumed that these trends have resulted in greater expectations of privacy.

This decision will not be the last word on the subject.  Other courts have reached the opposite conclusion, and the government certainly will appeal the ruling. Regardless of the ultimate outcome, Judge Leon makes an obvious point -- courts cannot analyze present-day expectations of privacy by reference to technology and cultural norms that existed over three decades ago.