Historical location data is crucial to law enforcement officials. Mr. Eckenwiler offered the example of drug investigations: A cellphone carrier can establish where a suspect met his supplier and how often he returned to a particular location. Likewise, location data can be vital in establishing people’s habits and preferences, including whether they worship at a church or mosque or whether they are present at a political protest, which is why, civil liberties advocates say, it should be accorded the highest privileges of privacy protection.
The decision could also bear implications for other government efforts to collect vast amounts of so-called metadata, under the argument that it constitutes “business records,” as in the National Security Agency’s collection of Verizon phone records for millions of Americans.
“It provides support for the government’s view that that procedure is constitutional, obtaining Verizon call records, because it holds that records are business records,” said Mr. Kerr, of George Washington University. “It doesn’t make it a slam dunk but it makes a good case for the government to argue that position.”