For the first time ever, a federal district court judge has ruled that the government must present a warrant based on “probable cause” in order to obtain historical cell phone tower location information from a wireless carrier. The government is still considering whether to appeal the decision, but this case nevertheless provides an example of some of the legal challenges posed by location-capable mobile phones.

All communications service providers are required to provide assistance and information to law enforcement pursuant to various federal statutes. However, these same statutes also require law enforcement to meet certain legal standards in order to obtain a carrier’s assistance—if this standard is not met, law enforcement’s request may not be “lawfully authorized” and the carrier’s assistance may be improper under the law.

Recently, law enforcement authorities have been increasingly turning to wireless carriers with requests for “real-time” location information for a subject’s mobile phone, as well as “historical” mobile phone location information, which refers to information that a carrier has stored in its billing, operations or traffic management systems and records, such as information about which towers and/or sectors a customer’s phone “touched” over the course of a call, etc.—in other words, information that would allow someone to reconstruct a customer’s location and movements during a call.

In various jurisdictions around the United States, the government has argued that a combination of the Stored Communications Act (SCA) and the Pen Register Statute—taken together—allows law enforcement to obtain real-time mobile phone location information under a lower legal standard based on “specific articulable facts,” rather than on the more stringent standard known as “probable cause.” The majority of federal courts that have addressed this issue have rejected the government’s theory and ruled instead that real-time location information requires a warrant based on probable cause. Nevertheless, some courts have accepted the government’s theory, and conflicting opinions can be found even within the same federal district.

The issue of mobile phone location information that is stored in a carrier’s records (“historical” information) is somewhat different, and until recently had not been looked at closely by the courts.

That changed earlier in 2008, when the government applied for a court order in the Western District of Pennsylvania that would have required a wireless carrier (Sprint Nextel) to disclose “transactional records” for a customer’s mobile phone, including all “historical cellular tower data, cellular tower site information … and sectors.” The government based its request on the lower “specific articulable facts” standard of the combined SCA/Pen Register Statute.

A five-judge panel of U.S. magistrate judges rejected the government’s request, ruling that, under the Fourth Amendment and all relevant statutes, the government could only obtain this information through a warrant based on probable cause. The government appealed, but U.S. District Judge Terrence McVerry issued an order affirming the magistrates’ decision.

Although this ruling is only binding in one federal district, this issue is likely to continue to come before other courts throughout the country, and these courts may follow or be influenced by this decision.