REUTERS/Jim Young A police officer casts a shadow on a U.S. flag during preparations for the Congressional Gold Medal ceremony honoring the Dalai Lama in the rotunda on Capitol Hill in Washington October 17, 2007. 
The practice is unlike nearly all other aspects of American judicial proceedings, where courts have held that search warrants eventually should be made public.
The thing is that getting permission for electronic surveillance techniques - including tracking metadata and gathering all cellphones connected to a cell tower - is easier than getting a search or wiretap warrant.
The Obama administration has argued in court that cellphone customers "have no privacy interest" in their location data.
Furthermore, most of the cases in question do not involve national-security matters - which led the National Security Agency to gather phone data on millions of Americans - but use many of the same surveillance methods.
Several judges and former prosecutors told the Journal that the ubiquitous confidentiality "makes it difficult for the public and
"Congress can't regulate what it can't see," Stephen Smith, a Houston magistrate judge who has written extensively on electronic surveillance, told the Journal. "In fact, it's difficult for me to find out what's going on in another district if the case is sealed."
The government contends that unsealing the records can reveal informants, cooperators, and the technical tools used in investigations, even after they are dropped or the suspect is apprehended.