For the first known time since the U.S. government began collecting data about Americans’ phone calls in bulk after the 9/11 attacks, a telecommunications company has questioned those surveillance activities in court, according to a judge’s opinion unsealed on Friday.

That company, whose name was redacted from the opinion, did not directly challenge the government’s right to make companies turn over “telephony metadata” — information about the phone numbers customers dial and the time, date and duration of such calls.

Instead, on Jan. 22, the company asked the Foreign Intelligence Surveillance Court (FISC), which has routinely issued orders approving such surveillance, to explain its legal reasoning in the wake of a recent decision by another federal court that ruled such metadata collection unconstitutional.

Proceedings in the FISC are often secret, and Friday's unsealing was the first time since the inception of bulk surveillance that one of the telecommunications companies targeted for such surveillance is known to have used the court itself to question those tactics.

In an order signed on March 20 but only unsealed on Friday, Judge Rosemary M. Collyer wrote that the National Security Agency’s bulk collection was legal and did not violate the Fourth Amendment’s prohibition against unreasonable search and seizures because Americans have no “reasonable expectation” that metadata, which they voluntarily reveal to their phone companies, will remain private.

“If a person who voluntarily discloses information can have no reasonable expectation concerning limits on how the recipient will use or handle the information, it necessarily follows that he or she also can harbor no such expectation with respect to how the Government will use or handle the information after it has been divulged by the recipient,” Collyer wrote.

She noted that two of her colleagues on the court and two other federal district courts have agreed with such reasoning, which relies on a 1979 Supreme Court case, Smith vs. Maryland, in which the justices approved of the authorities’ installation of a “pen register” to record a telephone company’s call data.

The unknown telecom’s decision to ask the court for an explanation was prompted by a December opinion by a federal judge in another case who ruled that the NSA’s bulk metadata collection was illegal and “almost Orwellian.”

“I cannot imagine a more 'indiscriminate' and 'arbitrary' invasion than this systematic and high-tech collection and retention of personal data on virtually every single citizen for purposes of querying and analyzing it without prior judicial approval,” wrote Judge Richard J. Leon of the District of Columbia District Court. “Surely, such a program infringes on 'that degree of privacy' that the founders enshrined in the Fourth Amendment.”

Leon ordered the NSA’s surveillance to cease but put a stay on his ruling to allow the government to appeal.

Lawyers for the unnamed telecom wrote that their petition for an explanation from the court “arises entirely” from Leon’s order, which “for the first time” questioned the legality of collecting such metadata in bulk.

Having received a routine order on Jan. 3 from the intelligence court to hand over its metadata to the National Security Agency, the lawyers wrote, “it is appropriate … [to] inquire directly of the Court into the legal basis for the … production order.”

Kurt Opsahl, a senior staff attorney at the Electronic Frontier Foundation, told Al Jazeera that the telecom’s petition was welcome but that he would have preferred “a more in-depth argument” against surveillance that presented the issues “a little more thoroughly.”

Lawyers for the telecom wrote in the petition that the company “has always acted in good faith” when complying with the court’s orders and would continue to do so.

The case before Leon, Klayman vs. Obama, was filed by a conservative activist and grew out of revelations published by the Guardian last summer that detailed wide and pervasive domestic surveillance by the U.S. government, including the collection of phone metadata from virtually every American phone customer.

Those revelations were first detailed in a secret April 2013 Foreign Intelligence Surveillance Court order, published that June, that compelled Verizon to turn over metadata from all of its customers and was leaked to the Guardian by former NSA contractor Edward Snowden. Such orders became regular after the government reportedly brought its phone metadata surveillance under the court’s supervision in 2006.

In her March ruling, unsealed Friday, Collyer wrote that the unprecedented size of the NSA’s metadata program did not matter, since the question was only whether a “particular user has a reasonable expectation of privacy.”

“Properly viewed on a user-by-user basis, the NSA telephony metadata program is consistent with Supreme Court precedent, which time and technology have not affected,” she wrote.

However, Collyer noted that parts of a 2012 Supreme Court decision, United States vs. Jones, which determined that the installation of a Global Positioning System device on a suspect’s car by police for 28 days was illegal, might “signal” that a majority on the court “may be ready to endorse a new mode of analysis” in Fourth Amendment cases.

Leon, relying on some of the opinions in the Jones case, endorsed a so-called “mosaic” theory — that the many discrete movements of the car, viewed in aggregate, constituted a privacy violation.

“I think that there’s actually a lot more that can be drawn from the Jones case, and when you have a majority of justices that have questioned how Fourth Amendment law had been applied, it’s putting out an invitation for that law to be developed, and this court declined to take up that invitation,” EFF's Opsahl said.

“Metadata is extraordinary information that can reveal amazing things about people, in a way, even more than content, and the [Supreme] Court is going to have to address that and think about how to apply the Fourth Amendment in an era when metadata is so revealing.”