A federal judge recently ruled that if someone has their cell phone turned on, their location data does not deserve protection under the Fourth Amendment, meaning law enforcement can track individuals without a search warrant.

New York magistrate judge Gary Brown decided in favor of Drug Enforcement Administration (DEA) agents who were seeking his approval over a warrant on a doctor who they suspected was being paid for issuing thousands of prescriptions. The warrant would have compelled the physician’s phone company to provide real-time tracking data from his cell.

Brown, certainly to the delight of police, issued a 30-page brief outlining his opinion that, by carrying a cell phone, someone is essentially waiving their Fourth Amendment right to due process.

“Given the ubiquity and celebrity of geolocation technologies, an individual has no legitimate expectation of privacy in the prospective of a cellular telephone where that individual has failed to protect his privacy by taking the simple expedient of powering it off,” Brown wrote.

“As to control by the user, all of the known tracking technologies may be defeated by merely turning off the phone. Indeed – excluding apathy or inattention – the only reason that users leave cell phones turned on is so that the device can be located to receive calls. Conversely, individuals who do not want to be disturbed by unwanted telephone calls at a particular time or place simply turn their phones off, knowing that they cannot be located.”

He goes on to suggest that because there are smartphone applications available that allow users to locate people in their area with similar interests, cell phone customers should not expect their inherent right to privacy to be observed.

“Given the notoriety surrounding the disclosure of geolocation data to retailers purveying soap powder and blue jeans to mall shoppers, the police searching for David Pogue’s iPhone and, most alarmingly, the creators and users of the Girls Around You app, cell phone users cannot realistically entertain the notion that such information would (or should) be withheld from federal law enforcement agents searching for a fugitive.”

The American Civil Liberties Union (ACLU) has long been a voice for the American people against governmental overreach and technological surveillance. Chris Soghoian, a principal technologist and senior policy analyst at the ACLU, wrote that Brown’s opinion was “ridiculous.”

“There is a big difference between location information you knowingly share with a select group of friends (or, in fact, the world) and information collected about you without your knowledge or consent,” he wrote.

Exactly how common this practice is throughout the law enforcement community is unclear but it has widely been reported that a Michigan police force tried to gain information about every single cell phone within the proximity of a labor protest.

Congressional leaders are currently considering two laws that would address how freely police are able to bug citizens. During an April hearing on Capitol Hill one detective told Senators that warrantless geolocation tracking is “essential to obtain in the early stages of investigations when probable cause has not yet been established.”

That attitude, and the wide potential for abuse this kind of law creates, has the ACLU alarmed.

“Someone might be happy to share their location with a few friends by ‘checking in’ using Foursquare while at a music festival, but not want law enforcement to access that same information,” Soghoian continued. “And, they would still reasonably expect that their location a week later at an Alcoholics Anonymous meeting or abortion clinic should remain private. Sharing location data isn’t and shouldn’t be all or nothing.”