Carter Page
© J. Scott Applewhite/AP PhotoThe Republicans’ memo, according to people who’ve seen it, claims the bureau inappropriately used a controversial dossier on alleged ties between Trump and Russians to get permission to spy on ex-Trump aide Carter Page.
The battle between the White House, FBI and Congress over a classified GOP memo alleging misconduct by bureau officials again pushes into the spotlight a hotly debated law governing how the government uses its most invasive surveillance powers.

The law, the Foreign Intelligence Surveillance Act, allows authorities to secretly obtain permission to covertly gather intelligence on suspected spies or terrorists on U.S. soil. Republicans say FBI officials acted improperly when they sought a court's approval under the law to spy on a former campaign adviser to President Donald Trump, and they want to release a classified memo they wrote on the subject.

The national security community and privacy advocates have long battled over the law, with Republicans and Democrats alike often criticizing aspects of FISA. But the latest controversy has played out along purely political lines.

Republicans' memo, according to people who've seen it, claims the bureau inappropriately used a controversial dossier on alleged ties between Trump and Russians to get permission to spy on the ex-Trump aide, Carter Page. The FBI said Wednesday the memo contains "material omissions of fact," and Democrats say it mischaracterizes classified intelligence to make its point.

Intelligence experts say the process to get a judge to approve an application under FISA is onerous, requiring multiple layers of approval within the FBI and Justice Department and stacks of evidence. Because the evidence is still classified, it's impossible to judge the FBI's case from the outside. But former FBI officials said if the bureau used the dossier to get a warrant under FISA, it would have had to provide other supporting evidence to get it through so many hoops at both agencies.

"If I wanted to make something up, I'd have to forge it and fool 80 people if it's about a U.S. person,'' said Robert Anderson, who retired in December 2015 as the FBI's No. 3 official after years overseeing counterintelligence.

"FISA warrants typically are big thick documents, 50-60 pages. If the Nunes memo about one is just 4 pages, you can bet it's a carefully picked bowl of cherries," former acting CIA Director John McLaughlin tweeted on Wednesday.

Marion "Spike" Bowman, a top FBI national security lawyer for more than a decade, said he would be skeptical of House Republicans' claims of misconduct by FBI officials if the bureau and Justice Department used their usual rigor. But he said he was concerned by the revelation that two FBI officials involved in the Russia probe had once traded anti-Trump text messages and about information in the texts that he thought suggested possible ethical lapses by other FBI officials.

"I don't know what happened," said Bowman, who retired in 2006. "But there's something that's wrong in this whole process."

The FISA process was enacted in 1978 after disclosures that former FBI Director J. Edgar Hoover and presidents from both parties had long used U.S. intelligence agencies to spy on political enemies and dissidents. The law was revised in 2008 to place limits on the controversial program of warrantless wiretaps initiated during the Bush administration and to legalize warrantless eavesdropping on Americans communicating with foreign surveillance targets.

Privacy advocates say the FISA law is so broad that authorities can obtain warrants with little probable cause. They have long complained that judges rarely reject applications - only 12 out of 35,434 in the law's first 35 years. FISA judges in recent years have rejected slightly more cases.

Proponents say that's because the system is designed to catch problematic applications before they even get to a FISA court.

Under FISA, an FBI agent first files an application, which must be approved by the agent's supervisor, the head of the field office and its top lawyer. Supervisory agents and lawyers go over the application at headquarters in Washington, and the FBI's head of counterintelligence, deputy director and director also review it.

If FBI top brass sign off, the Justice Department does its own review before an application goes before the Foreign Intelligence Surveillance Court, where lawyers review it to determine if it merits a top-secret hearing before one of the revolving panel of judges, who are appointed by the chief justice of the Supreme Court.

The FISA judges are known to grill the FBI supervisory agents who appear before them to testify in support of the applications, Anderson said.

"In nuclear proliferation Chinese cases, you'd be there for an hour," Anderson says. "What's this mean? What's this piece of technology? Why do we care? How do you know that's his cellphone?"

Bowman said he might have approved an application for a surveillance warrant that referenced a document like the dossier - which was compiled by former British spy Christopher Steele on behalf of the firm Fusion GPS, which received funding from Democrats to research Trump - but only if there was plenty of supplemental evidence.

Michael Rochford, a former head of the FBI's counterespionage section, also said he would have been skeptical.

"If that would have appeared on my desk, I would have thrown it out. I wouldn't let any agent come to me with a FISA application based on hearsay from GPS Fusion," Rochford said.

Rochford said that if the FBI knew Steele was being paid to compile the dossier, or who was paying for it, that information should have been disclosed to the judge.

"The idea that he's being paid is important, and you need to report it as quickly as possible," the former agent said. "Your obligation is to immediately inform the judge that your validation of the source has changed. I hope the bureau didn't lapse."

FBI officials have not commented on any aspect of the FISA application, including whether they disclosed the source of the dossier.