In a patient, somewhat defensive letter to Senators Patrick Leahy and Chuck Grassley, Reggie Walton, the presiding judge of the classified Foreign Intelligence Surveillance Court, offered details on how the court works. One key ruling will soon become public; other critical details are under consideration for release. It's a letter that might have seemed impossible three months ago, but now reinforces that the judicial and legislative branches appear much more willing to detail NSA surveillance than the branch of the government that houses the NSA.

Before we get to the details of that letter, it's worth mentioning another, which the Director of National Intelligence, James Clapper, sent to Senator Ron Wyden of Oregon answering some of his questions about the surveillance systems. Among the revelations in in it were specific timelines on data collection (May 2006 for phone records) and the use of location data (the NSA doesn't collect it). Clapper also suggested that concerns over NSA errors are overblown.

Since the telephony metadata collection program under [Patriot Act] Section 215 was initiated, there have been a number of compliance problems that have been previously identified and detailed in reports to the Court and briefings to Congress as a result of Department of Justice reviews and internal NSA oversight. However, there have been no findings of any intentional or bad-faith violations.

These problems generally involved human error or highly sophisticated technology issues related to NSA's compliance with particular aspects of the Court's orders.

Wyden responded today by suggesting that suggested today that the violations are "significantly more troubling" than Clapper suggests. 

The details of those violations remain buried within Walton's secret court. Leahy and Grassley, the ranking members on the Senate's Judiciary Committee, earlier this month sent Walton a series of questions seeking to publicly clarify the FISC's process in advance of a Judiciary hearing tomorrow. (That hearing begins at 9 a.m.) While Walton obviously didn't dwell on the classified details of specific cases, the process he did provide extensive detail on how the government presents its requests for surveillance authority.

It's somewhat odd that the senators felt the need for such detail. In his letter, Clapper also wrote:

[I]t is not correct to say that [the Patriot Act] had been "secretly reinterpreted." The relevant materials were, of course, properly classified to protect sensitive intelligence collection activity, but, as Congress required, the Executive Branch fully and repeatedly briefed the Intelligence and Judiciary Committees of both Houses about the program and timely provided copies of the relevant classified documents to the Committees.

Clearly, members of the Senate Judiciary Committee still had some questions.

One of the more interesting responses it got from Walton involves those instances in which a party that isn't the government has presented arguments to the court. Normally, the FISC is an exchange between the government's attorneys and court judges and staff. Particularly recently, that's changed. At the court's still-new public docket, details of cases involving outside parties are revealed. Several we've mentioned before — lawsuits from the ACLU and the EFF, for example, the latter of which seeks to release the court's ruling that the NSA had violated the Fourth Amendment.

According to Walton, in only one case was a nongovernmental party "sought to substantively contest a directive from the government." That was a 2008 decision in which Yahoo tried (unsuccessfully) to challenge a ruling by the court. Following a request from Yahoo earlier this year, the FISC asked the Department of Justice to offer a timeline for declassifying the documents. In a letter to the court addressed Monday, the Department set that deadline: September 27, 2013. It is safe to assume that it will become public late that afternoon.

Walton's letter primarily addressed how the system works. As we knew, the judges on the court work in week-long shifts. Walton describes what happens when one of the eleven judges is presented with a request. (FISA, below, refers to the Foreign Intelligence Surveillance Act and amendments to it passed in 2008.)

Upon the Court's receipt of a proposed application for an order under FISA, a member of the Court's legal staff reviews the application and evaluates whether it meets the legal requirements under the statute. As part of this evaluation, a Court attorney will often have one or more telephone conversations with the government to seek additional information and/or raise concerns about the application. A Court attorney then prepares a written analysis of the application for the duty judge, which includes an identification of any weaknesses, flaws, or other concerns.

The judge reviews the staff evaluation and determines the course of action. One possibility is a hearing with the government's representative, though a hearing is not mandatory. The judge can also request more information or approve the request outright. If the judge seeks more information or wants to apply conditions to approval, the government can request a hearing, or it can simply withdraw the application. Walton notes that such withdrawals aren't included in the statistics sent to Congress. The letter also indicates that "a significant percentage of cases" result in requests for more information from the government, though that percentage isn't specified.

The annual statistics provided to Congress by the Attorney General pursuant to 50 U.S.C. §§ 1807 and 1862(b) — frequently cited to in press reports as a suggestion that the Court's approval rate of applications is over 99% — reflect only the number of final applications submitted to and acted on by the Court. These statistics do not reflect the fact that many applications are altered prior to final submission or even withheld from final submission entirely, often after an indication that a judge would not approve them.

Some government requests differ slightly from that procedure, including approval for collection of telephone call metadata under Section 215 of the Patriot Act and internet communication collection under Section 702 of the FISA amendments. In the case of metadata, for example, the staffer conducting the review spends a "greater amount of time reviewing and preparing a written analysis of such an application."

This was precisely the issue with which Clapper downplayed mistakes in application and Wyden suggested more significant problem. For now, we'll have to simply guess at the reality. Until some future letter from the FISC emerges.