US federal law enforcement officials will have to get a search warrant before getting engaged into mobile phone surveillance. The US justice department new policy emerges amid concerns from privacy groups. Moreover, it judges that cell-site simulator technology is infringing on privacy rights.

The technology in question is dubbed Stingray, looks like a suitcase-sized device and is able to sweep up basic mobile phone data by tricking phones in the area to believe that it’s a cell tower. The collected data is transmitted to the police in order to help determine the location of a phone without the user even using it to call or text. It should be noted that this technology doesn’t collect the content of communications.

Despite federal law enforcement officials describing the technology as a very important tool to catch criminals, privacy groups have raised concerns about the collection of mobile phone data of other people who happen to be in a particular area. These concerns are now being addressed by the justice department’s new policy, which applies only to federal agencies within the department.

Aside from requiring a warrant in most circumstances, except for emergencies, the policy also orders the law enforcement authorities to delete information that has been collected after the investigation.

The privacy campaigners hope that this policy could act as a blueprint for state and local law enforcement agencies, but how broad an impact of this new policy will be remains to be seen, because it doesn’t actually directly affect local police agencies.

The industry observers point out that the use of the technology has spread widely among local police departments, who withhold materials or heavily censor documents that they do provide. Local departments have faced scrutiny from judges about how they deploy the surveillance equipment, even despite the fact that they have often insisted that FBI non-disclosure agreements limit what they can say.

The American Civil Liberties Union called this recent policy a good first step: even though it did not cover federal agencies outside the justice department or local police, it is going to “let the air out of state law enforcement’s argument that a warrant shouldn’t be required”. The ACLU also called on the justice department to close remaining loopholes.