Since this spring’s blink-and-you-missed-it debate over reauthorization of several controversial provisions of the Patriot Act, Senators Ron Wyden (D-OR) and Mark Udall (D-CO) have been complaining to anyone who’d listen about a “Secret Patriot Act“—an interpretation of one of the law’s provisions by the classified Foreign Intelligence Surveillance Court granting surveillance powers exceeding those an ordinary person would understand to be conferred from the text of the statute itself. As I argued at the time, there is an enormous amount of strong circumstantial evidence suggesting that this referred to a “sensitive collection program” involving cell phone location tracking—potentially on a mass scale—using Patriot’s “Section 215” or “business records” authority.

Lest anyone think they’d let the issue drop, Wyden and Udall last week released a sharply-worded letter to Attorney General Eric Holder, blasting the Justice Department for misleading the public about the scope of the government’s surveillance authority. The real audience for an open letter of this sort, of course, is not the nominal recipient, but rather the press and the public. Beyond simply reminding us that the issue exists, the letter confirms for the first time that the “secret law” of which the senators had complained does indeed involve Section 215. But there are some additional intriguing morsels for the attentive surveillance wonk.

The letter focuses particularly on “highly misleading” statements by Justice Department officials analogizing Section 215 powers to grand jury subpoenas. “As you know,” Wyden and Udall write, “Section 215 authorities are not interpreted in the same way that grand jury subpoena authorities are, and we are concerned that when Justice Department officials suggest that the two authorities are ‘analogous’ they provide the public with a false understanding of how surveillance law is interpreted in practice.”

Now, this is a little curious on its face. Ever since the original debate over the passage of the Patriot Act, its defenders have tried to claim that a variety of provisions allowing the FBI to more easily obtain sensitive records and documents were no big deal, because grand juries have long enjoyed similarly broad subpoena powers. The comparison has been specious all along: grand juries are an arm of the judicial branch designed (at leas in theory) to serve as a buffer between the power of prosecutors and the citizenry. It exists for the specific purpose of determining whether grounds for a criminal indictment exist, and is granted those broad subpoena powers precisely on the premise that it is not just another executive branch investigative agency. To argue, then, that it would make no difference if the FBI or the police could secretly exercise the same type of authority is to miss the point of how our system of government is meant to work in a pretty stunning way. It’s akin to suggesting that, since juries can sentence people to life in prison, it would be no big deal to give the president or the director of the FBI the same power.

That’s not what Wyden and Udall are stressing here, however. Rather, they seem to be suggesting that the scope of the 215 authority itself has been secretly interpreted in a way that goes beyond the scope of the grand jury subpoena power. Now that ought to be striking, because the grand jury’s power to compel the production of documents really is quite broad. Yet, what Wyden and Udall appear to be suggesting is that there is some kind of limit or restriction that does apply to grand jury subpoenas, but has been held by the secret court not to apply to Section 215 orders. One possibility is that the FISC may have seen fit to issue prospective 215 orders, imposing an ongoing obligation on telecommunications companies or other recipients to keep producing records related to a target as they’re created, rather than being limited to records and documents already in existence. But given the quantity of evidence that already suggests the “Secret Patriot Act” involves location tracking, I find it suggestive that the very short list of specific substantive limits on grand jury subpoena power in the U.S. Attorneys’ Manual includes this:

It is improper to utilize the grand jury solely as an investigative aid in the search for a fugitive in whose testimony the grand jury has no interest. In re Pedro Archuleta, 432 F. Supp. 583 (S.D.N.Y. 1977); In re Wood, 430 F. Supp. 41 (S.D.N.Y. 1977), aff’d sub nom In re Cueto, 554 F.2d 14 (2d Cir. 1977). … Since indictments for unlawful flight are rarely sought, it would be improper to routinely use the grand jury in an effort to locate unlawful flight fugitives.

As the manual makes clear, the constraints on the power of the grand jury generally are determined by its purpose and function, but locating subjects for the benefit of law enforcement (rather than as a means of securing their testimony before the grand jury) is one of the few things so expressly and specifically excluded. Could this be what Wyden and Udall are obliquely referring to?

On a possibly related note, the Director of National Intelligence’s office sent Wyden and Udall a letter back in July rebuffing his request for information about the legal standard governing geolocation tracking by the intelligence community. While refusing to get into specifics, the letter explains that “there have been a diverse set of rulings concerning the quantum of evidence and the procedures required to obtain such evidence.” Now, a bit of common sense here: it is inconceivable that any judge on the secret court would not permit cell phone geolocation tracking of a target who was the subject of a full-blown FISA electronic surveillance warrant based on probable cause. There would be no “diversity” if the intelligence agencies were uniformly using only that procedure and that “quantum of evidence.” This claim only makes sense if the agencies have sought and, under some circumstances, obtained authorization to track cell phones pursuant to some other legal process requiring a lower evidentiary showing. (Again, you would not have “diversity” if the court had consistently responded to all such requests with: “No, get a warrant.”)

The options here are pretty limited, because the Foreign Intelligence Surveillance Act only provides for a few different kinds of orders to be issued by the FISC. There’s a full electronic surveillance warrant, requiring a probable cause showing that the target is an “agent of a foreign power.” There’s a warrant for physical search, with the same standard, which doesn’t seem likely to be relevant to geotracking. The only other real options are so-called “pen register” orders, which are used to obtain realtime communications metadata, and Section 215. Both require only that the information sought be “relevant” to an ongoing national security investigation. For pen registers, the applicant need only “certify” that this is the case, which leaves judges with little to do beyond rubber-stamping orders. Section 215 orders require a “statement of facts showing that there are reasonable grounds” to think the information sought is “relevant,” but the statute also provides that any records are automatically relevant if they pertain to a suspected “agent of a foreign power,” or to anyone “in contact with, or known to” such an agent, or to the “activities of a suspected agent of a foreign power who is the subject of [an] authorized investigation.” The only way there can logically be “a diverse set of rulings” about the “quantum of evidence and the procedures required” to conduct cell phone location tracking is if the secret court has, on at least some occasions, allowed it under one or both of those authorities. Perhaps ironically, then, this terse response is not far short of a confirmation.

In criminal investigations, as I noted in a previous post, the Justice Department normally seeks a full warrant in order to do highly accurate, 24-hour realtime location, though it is not clear they believe this is constitutionally required. With a court order for the production of records based on “specific and articulable facts,” they can get call records generally indicating the location of the nearest cell tower when a call was placed—a much less precise and intrusive form of tracking, but one that is increasingly revealing as providers store more data and install ever more cell towers. For realtime tracking that is less precise, they’ll often seek to bundle a records order with a pen register order, to create a “hybrid” tracking order. Judges are increasingly concluding that these standards do not adequately protect constitutional privacy interests, but you’d expect a”diverse set of rulings” if the FISC had adopted a roughly parallel set of rules—except, of course, that the standards for the equivalent orders on the intelligence side are a good deal more permissive. The bottom line, though, is that this makes it all but certain the intelligence agencies are secretly tracking people—and potentially large numbers of people—who it does not have probable cause to believe, and may not even suspect, are involved in terrorism or espionage. No wonder Wyden and Udall are concerned.