In the first ruling of its kind, a federal magistrate judge held that the government must obtain a search warrant to collect the content of a telephone call even when that content is dialed digits like bank account numbers, social security numbers, or prescription refills. The decision from Magistrate Judge Smith in Houston closely followed the reasoning outlined in an amicus brief from EFF and the Center for Democracy and Technology (CDT).

The Texas judge invited EFF to file the brief in response to requests from government investigators to use a "pen register" or "trap and trace device" to collect all numbers dialed on a phone keypad after a call has been connected. Investigators can typically get "pen/trap" orders under a legal standard much lower than the "probable cause" required for a typical phone-tapping warrant because only phone numbers used to connect the call are collected not the content of the phone call itself.

However the judge found that when it comes to dialed numbers that represent call content, federal statutes require that investigators either get a probable cause warrant or use filtering technology to ensure that only dialed phone numbers are collected. In fact, according to the court, "Congress ordered law enforcement to do just that 12 years ago, yet the court notes that the government's current practice is to collect all dialed digits without using any filtering technology."

In the same opinion, Judge Smith also rejected a new government request to track the location of someone's cell phone without a warrant. EFF has briefed two other courts on the cell-tracking issue, which has been a continuing controversy since Judge Smith and another judge in New York first published decisions on the issue. Those decisions revealed that government investigators had routinely been tracking cell phones for years without getting warrants based on frivolous legal arguments.