New data from law enforcement agencies across the country has confirmed what EFF has long been afraid of: while police are routinely using cell phone location tracking information, only a handful of agencies are bothering to obtain search warrants.

Since 2005, we've been beating the drum loudly, warning that the government's attempts to track a person's physical location through their cell phone requires a search warrant. As we've said again and again, because cell phone tracking can give the government a snapshot of a person's life through their movements, a search warrant is necessary to safeguard against privacy intrusions.

Now new data -- obtained from a coordinated FOIA request by the ACLU -- shows just how pervasive cell phone tracking is throughout the United States. The ACLU obtained 5,500 pages of records from over 200 different law enforcement agencies. The records revealed that most law enforcement agencies are using location tracking information routinely, with only 10 out of the more than 200 claiming they had not tracked cell phones.

And even more troubling, the records demonstrate that different agencies use different standards to obtain this information, with only a few agencies obtaining search warrants in order to track. It looks like local law enforcement agencies are taking their lead from the federal government, who has been using cell location data obtained without a search warrant for years. The case of Antoine Jones is one example. If his name sounds familiar, its because in January of this year, the U.S. Supreme Court ruled in a landmark decision that the warrantless surveillance of Jones for 28 days through a GPS device violated the Fourth Amendment. Now unable to use the GPS data, the government is turning to cell location data which it also obtained without a search warrant. In another case, the government has appealed to the Fifth Circuit Court of Appeals to reverse the decision of a magistrate judge - who we supported in an amicus brief - that required the government to obtain a search warrant in order to obtain cell tracking information. A magistrate judge in Massachusetts (PDF), and a district court judge in Maryland (PDF) have recently reached the opposite conclusion, ruling that the government didn't need a search warrant to obtain cell location data.

To civil liberties organizations like us and the ACLU, the privacy implications of obtaining this data without a search warrant are obvious and troubling. But it seems that at least one law enforcement agency recognized the likely public outrage too. The New York Times reports that the Iowa City Police Department warned officers in a training manual not to "mention to the public or the media the use of cellphone technology or equipment used to locate the targeted subject,” and even to keep them out of police reports.

But the story doesn't just end with location data. Because once the police find the phone they've been tracking, its getting easier (and more frequent) for them to search the contents of the phone without a warrant, and to obtain reams of your personal data in minutes. A video demonstration posted online by Micro Systemation, a Swedish mobile forensics company that sells its devices to law enforcement agencies, demonstrated how easily police can crack a cell phone's security and suck all of the data out in seconds. Unsurprisingly, once the video went viral last week, it was pulled from YouTube.

And as we've noted before, recent court decisions have allowed the police to search an arrested person's cell phone "incident to arrest" without a warrant, or any reason to believe they will find anything incriminating on it. The Seventh Circuit Court of Appeals is the latest court to authorize this practice, issuing a decision (PDF) in February finding no Fourth Amendment violation in a warrantless search of a cell phone of an arrested person. The police have now been armed to turn any pretextual arrest - say, an Occupy Wall Street arrest for disorderly conduct - into a cell phone fishing expedition, getting access to your calendar, contacts, emails, text messages, voicemails and reading and web browsing history.

All this gloom and doom can be fixed in two ways. First, courts need to recognize that the Fourth Amendment prohibits pervasive and sustained government surveillance unless the police get a search warrant. For centuries, the government's biggest limitation was technological; it was difficult - if not impossible - to follow a person for days at a time. But with surveillance tools becoming smaller and cheaper, its easier for the government to use surveillance information from our own cars to investigate mundane, non-violent crimes. The Fourth Amendment needs to keep up with the changes in technology in order for its longstanding privacy protections to have meaning.

Second, Congress needs to step up and update our electronic privacy laws. The law that governs cell phone location data - the Electronic Communications Privacy Act ("ECPA") - is more than 25 years old, enacted in a time where cell phones were far from ubiquitous. The law has been unable to keep up with the rapid technological changes that have occurred since 1986, and the conflicting court opinions on the constitutionality of warrantless cell phone location tracking noted above is the end result. It's time for Congress to reexamine the law and bring it in line with our expectations of privacy today.

You can do your part by getting informed and checking out the ACLU's location data map to figure out whether the cops where you live use location tracking data. Regardless of whether or not you live in a state where the cops track, you can tell Congress that its time to fix our broken and ancient technology laws by signing our action alert, and taking a stand to protect our locational privacy from the prying eyes of the government.