Most Foreign Intelligence Surveillance Court opinions governing National Security Agency surveillance are classified, but the panel’s top judge disputed the idea that his court is a rubber-stamp for President Obama in an unclassified memo to Senate Judiciary Chairman Patrick Leahy, D-Vt.

Presiding Judge Reggie B. Walton described an involved process for considering NSA requests, with the court indicating the likelihood of success or failure to government attorneys at each step of the way, to allow attorneys to revise the application or make counterarguments.

“In some cases, the government may decide not to submit a final application, or to withdraw one that has been submitted, after learning that the judge does not intend to approve it,” Walton wrote in the Monday letter.

“The annual statistics provided to Congress by the Attorney General pursuant to [U.S. law] — frequently cited to [sic] in press reports  as a suggestion that the Court’s approval rate of applications is over 99 percent  – 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,” Walton continued.

Leahy prompted the memo by asking in a June 18 letter to Walton for a description of the process the court uses when considering applications pertaining to  “electronic surveillance,” “access to business records,” and “submissions from the government under Section 702 of FISA.”

Walton said that requests for phone records in bulk undergo a “more exacting” review. “The attorney who reviews the application spends a  greater amount of time reviewing and preparing a written analysis of such an application, in part because the Court has always required detailed information about the government’s implementation of this authority,” the judge wrote.

“The judge likewise typically spends a greater amount of time than he or she normally spends on an individual application, carefully considering the extensive information provided by the government and determining whether to seek more information or hold a hearing before ruling on the application,” he also said.

The FISA court received widespread public attention after then-NSA contractor employee Edward Snowden leaked information on the agency’s surveillance tactics to The Daily Mail’s Glenn Greenwald.

“The National Security Agency is currently collecting the telephone records of millions of US customers of Verizon, one of America’s largest telecoms providers, under a top secret court order issued in April,” Greenwald wrote.

“The secret Foreign Intelligence Surveillance Court granted the order to the FBI on April 25, giving the government unlimited authority to obtain the data for a specified three-month period ending on July 19,” he said.

Director of National Intelligence James Clapper said that Greenwald’s report “contain[ed] numerous inaccuracies.”

“[T]he United States Government does not unilaterally obtain information from the servers of U.S. electronic communication service providers. All such information is obtained with FISA Court approval and with the knowledge of the provider  based upon a written directive from the Attorney General and the Director of National Intelligence,” the DNI added in a fact sheet.

“In short, Section 702 facilitates the targeted acquisition of foreign intelligence  information concerning foreign targets located outside the United States under court  oversight. Service providers supply information to the Government when they are lawfully required to do so.”