Glenn Greenwald has revealed what he described last month as "the most important in the archive" of documents leaked by former NSA contractor Edward Snowden. The Intercept reports that the NSA and FBI have been spying on law-abiding Muslim-Americans — including lawyers, academics, civil rights activists, and a political candidate — possibly without warrants, under the pretext of the Foreign Intelligence Surveillance Act. The new document marks the first time individual US citizens have proof that they have been targeted by domestic surveillance, and could give them the legal standing to sue the government.

The Intercept has been able to identify five targets from an NSA spreadsheet that lists thousands of suspects. The targets, all Muslim-Americans, include Faisal Gill, who was an advisor for the Bush administration’s Department of Homeland Security; Agha Saeed, a civil rights activist who was formerly a political science professor at California State University; Nihad Awad, executive director of the Council on American-Islamic relations; Asim Ghafoor, a lawyer who has represented clients in cases connected to terrorism; and Hooshang Amirahmadi, a professor at Rutgers University. All have led "highly public, outwardly exemplary lives," according to The Intercept, and all deny involvement in terrorism or espionage.

The spreadsheet lists 7,485 email addresses of individuals monitored between 2002 and 2008. According to The Intercept, 202 of the addresses belong to Americans, while another 5,501 have their nationality marked as "unknown" or have the field left blank. The document is named "FISA recap" in reference to the Foreign Intelligence Surveillance Act. According to that act, the US government must show the Foreign Intelligence Surveillance Court that it believes Americans are both agents of terrorist organizations or foreign powers, and "are or may be" actively engaged in or abetting terrorism, espionage, or sabotage.

Under FISA, the government is meant to renew its authorization to snoop on Americans every 90 days. The document revealed as a part of the Snowden leaks indicates that the surveillance had been approved to continue after that time, suggesting that some of the individuals targeted may have been monitored illegally. Both the National Security Agency and the Office of the Director of National Intelligence stress that surveillance of US citizens is always conducted with a warrant "except in exceptional circumstances."

In an internal memo, the name "Mohammed Raghead" was used as a placeholder surveillance target

It's not clear why the five Muslim-American men were targeted by the government for surveillance, but Asim Ghafoor believes he was monitored for his religion and cultural background. "I believe that they tapped me because my name is Asim Abdur Rahman Ghafoor, my parents are from India, I travelled to Saudi Arabia as a young man, and I do the pilgrimage," the lawyer tells The Intercept. Greenwald likens the attitudes towards Muslims in US government agencies to the anti-communist "hysteria of the McCarthy era," and says that blatant prejudice against Muslim-Americans is obvious in the Snowden files. One document from 2005 shows security personnel how to format memos designed to obtain FISA surveillance rights. As a placeholder, the target's name is filled in as "Mohammed Raghead."

The Department of Justice and the Office of the Director of National Intelligence strongly deny that the US monitors activists simply because of their race, religion, or dissenting views. In a statement released after the publication of The Intercept's report, the agencies say it is "entirely false" that US intelligence would conduct electronic surveillance because of these factors. The agencies do not, however, specifically mention the article in question or refute that anyone named by The Intercept was under surveillance. Instead, the agencies note that a court order based on probable cause is more than often required to begin surveillance, writing that "a person who the court finds is an agent of a foreign power under this rigorous standard is not exempted just because of his or her occupation."

Previously, it's been revealed that US intelligence agencies routinely tapped the phones of foreign allies like German chancellor Angela Merkel. The revelation chilled relations between the US and Europe, though President Barack Obama has denied that he knew of any surveillance of Merkel. Inappropriate surveillance of Americans also helped spark the formation of the Church Committee, one of the most important reform efforts in recent memory. In 1975 and 1976, Church Committee reports detailed how the FBI had closely watched and attempted to discredit Dr. Martin Luther King, Jr., along with people sometimes only tangentially associated with black nationalist, white supremacist, or communist groups.

Update July 9th, 9:25AM ET: this article has been updated to include comment from the DOJ and the DNI's office.

Additional reporting by Sam Byford, Adi Robertson, and Jacob Kastrenakes.