A federal judge in Illinois has recently taken the unusual step of issuing three new stringent requirements for the government when it wants to deploy cell-site simulators. The move aims to protect the Fourth Amendment rights of innocent bystanders against unreasonable search and seizure.

Of course, for now, this order only applies to this one judge in the Northern District of Illinois.

These new stingray requirements come just about a month after the Department of Homeland Security imposed its own warrant requirement, following a similar move by the Department of Justice.

Not only can stingrays be used to determine location by spoofing a cell tower, but they can also be used to intercept calls and text messages. Once deployed, the devices intercept data from a target phone as well as information from other phones within the vicinity.

As part of an ongoing drug case, US Magistrate Judge Iain Johnston told prosecutors recently that they will now have to fulfill three distinct requirements before he will sign off on the use of the invasive surveillance devices, as a way to protect the privacy of those who happened to be near a surveillance target. The memorandum opinion came down earlier this month as part of a largely sealed ongoing drug investigation, the details of which the judge described as "unsurprising."

What is surprising is Judge Johnston’s order to compel government investigators to not only obtain a warrant (which he acknowledges they do in this case), but also to not use them when "an inordinate number of innocent third parties’ information will be collected," such as at a public sporting event.

This first requirement runs counter to the FBI’s previous claim that it can warrantlessly use stingrays in public places, where no reasonable expectation of privacy is granted.

Second, the judge requires that the government "immediately destroy" collateral data collection within 48 hours (and prove it to the court).

Finally, Judge Johnston also notes:

Third, law enforcement officers are prohibited from using any data acquired beyond that necessary to determine the cell phone information of the target. A cell-site simulator is simply too powerful of a device to be used and the information captured by it too vast to allow its use without specific authorization from a fully informed court. Minimizing procedures such as the destruction of private information the United States has no right to keep are necessary to protect the goals of the Fourth Amendment.

Mum's the word

Nathan Swanson, a Saint Louis-based criminal defense attorney, told Ars that these new limits are notable.

"Here, it seems [prosecutors] are saying that the known individual has an unknown cell phone number," he e-mailed Ars.

"They are trying to find the identifiers for that one individual’s cell phone. They know they’ll end up with a bunch of innocent people, who have no relevance. So the judge is saying do everything you can to limit that."

For years, federal and local law enforcement have tried to keep the existence of cell-site simulators a secret while simultaneously upgrading their capabilities. Over the last year, as the devices have come under increased scrutiny, new information about the secretive devices has come to light.

Ars has previously reported that while stingrays have been used at the local level for serious violent crimes, they have also been used to investigate ATM robberies, and even 911 hangups.

UPDATE Friday 7:05pm ET: Rachel Levinson-Waldman, an attorney and legal scholar at New York University, told Ars that this may be a landmark legal opinion.

She writes:

I think this may actually be one of the first decisions regarding stingrays (as the judge himself suggests). As I'm sure you know, applications for court orders for Stingrays have often been fairly misleading, so as not to disclose that the devices being used. And when it has looked as though their use is going to be revealed, prosecutors have dropped the charges. So I think this is the first time, or close to it, that a judge has had a chance to address them directly in a published order. That alone is striking. I also think the order is operating on two levels simultaneously. On the surface, the judge is directing the order at the government, but the second level is directed at his colleagues in the judiciary; he's using the order as a platform to urge other judges to take the time to understand what stingrays really are. It's kind of like he's subtweeting.

Meanwhile, Brian Owsley, himself a former magistrate judge, and a current law professor at the University of North Texas, concurred.

"This is a well-reasoned opinion that acknowledges that even the Government in September of this year has essentially acknowledged that probable cause is the standard that should be utilized even though it does not necessarily admit that it the appropriate," he e-mailed. "Indeed for the government to admit that is the appropriate standard would mean that so many prior applications were done with less than the appropriate standard."