A federal appeals court in Atlanta last week handed down a ruling that, if eventually affirmed by the Supreme Court, will greatly strengthen individual privacy rights by limiting government intrusions, such as bulk collection of telephone records by the National Security Agency (NSA).

The 11th Circuit Court of Appeals held that the Fourth Amendment prohibition against "unreasonable searches and seizures" applies to records held by providers of cell phone services that identify the geographic location where each cell phone call is made.

The opinion by Judge David Sentelle very carefully positioned this finding to be at variance with decisions in two other circuit courts on similar issues, virtually guaranteeing Supreme Court review. The opinion thus opens the door to a welcome and much needed debate before the Supreme Court on the reach of the Fourth Amendment in protecting individual privacy.

It gives the court an opportunity to overturn or greatly modify the current legal basis for limiting privacy, the 1979 decision in Smith vs. Maryland that records of telephone calls are not covered by the Fourth Amendment because telephone subscribers have no "reasonable expectation" that such records are private property.

That case provides the legal underpinning for laws, such as the Patriot Act, that allow the U.S. Department of Justice and local law enforcement authorities to obtain a person's telephone call records, bank records and other personal transaction records without having to persuade a judge that there is "probable cause" to believe a law has been broken.

The NSA and the secret Foreign Intelligence Surveillance Court have relied on Smith vs. Maryland and the Patriot Act to justify the bulk collection of American telephone call records on the possibility that some records might eventually be needed in a terrorism investigation.

The NSA's overreach represents just one facet of the privacy problems created today by technology that was not available for general use when Smith was decided. Another is described by what has been called the "mosaic theory" of privacy, in which bits of information that might be readily available in public can be put together to create a picture of a person's life in which recognized privacy rights are violated.

For example, in 2012 the Supreme Court, in U.S. vs. Jones, held that the Fourth Amendment was violated when law enforcement officers put a GPS device on a car and left it there for 28 days without court permission.

The court rejected the argument that because the car could be seen any time it was on the street, the driver had no reasonable expectation of privacy. In a concurring opinion, Justice Sonia Sotomayor noted that such "monitoring generates a precise, comprehensive record of a person's public movements that reflects a wealth of detail about her familial, political, professional, religious, and sexual associations."

In his opinion in U.S. vs. Quartavious Davis, Judge Sentelle cited the Jones case in support of a finding that cell phone tracking information creates a mosaic picture that is an invasion of privacy unless carried out with permission of a court, as required by the Fourth Amendment.

Quartavious Davis was a member of a robbery gang whose conviction turned on eyewitness identification and testimony by other members of the gang. Judge Sentelle upheld his conviction but found that law enforcement should have gone to court to track his cell phone use.

Now it is up the Supreme Court to address the critical question Judge Sentelle raised regarding Fourth Amendment privacy protections.