Fifteen former staff members of a Watergate-era intelligence watchdog committee have jointly written to President Barack Obama and Attorney General Loretta Lynch urging them to extend leniency to NSA whistleblower Edward Snowden. Signed by a group of members of the Church committee, a special Senate body that investigated illegal governmental operations by the CIA and other intelligence agencies in the 1970s, the letter calls on Obama to resolve the "Snowden matter" and end his "untenable exile in Russia, which benefits nobody".

Currently residing in Moscow, the former NSA contractor has been in exile since 2013 when he leaked thousands of classified documents revealing the extensive mass surveillance programmes in the US and UK. Snowden faces charges brought under the 1917 Espionage Act and could face up to 30 years in prison, if convicted.

The letter's authors argued that although Snowden's disclosures were illegal, they did trigger a debate regarding surveillance and accountability and prompt bipartisan reforms.

"Whether or not these clear benefits to the country merit a pardon, they surely do counsel for leniency," the signatories wrote. "There is no question that Snowden broke the law. But previous cases in which others violated the same law suggest leniency.

And most importantly, Snowden's actions were not for personal benefit, but were intended to spur reform. And they did so."

The signatories noted earlier cases of leniency shown by Obama's and previous administrations towards others who made illegal disclosures or even destroyed classified information including National Security Adviser Sandy Berger and CIA directors David Petraeus and John Deutch.

Sandy Berger, who broke the law by removing and destroying several highly classified documents from the National Archives requested by the 9/11 Commission, was allowed to plead guilty to a misdemeanour, and received a fine and probation.

Petraeus violated the law and his obligation to protect national security information by giving notebooks documenting secret military and intelligence operations to his biographer and lover. He also shared classified information with reporters and lied to the FBI about his actions, they noted. However, he was allowed to plead guilty to one misdemeanour and received no jail time. He is now being considered by President-elect Donald Trump to become US secretary of state.

"In all of these cases, recognition of the public service the individuals had provided weighed against strict enforcement of the law, to come to a fair and just result," they wrote.

Edward Snowden
NSA former intelligence contractor Edward Snowden is seen via live video link from Russia on a computer screen during a parliamentary hearing at the Council of Europe in Strasbourg. Frederick Florin/AFP/Getty Images

They also mentioned that the Church Committee, officially known as the US Senate Select Committee to study government operations with respect to intelligence activities, was responsible for disclosures revealing abuses of power by six US presidents from both parties including Franklin Roosevelt and Richard Nixon.

Some of the other numerous abuses unearthed by the committee include the NSA obtaining copies of every telegram leaving the US for 30 years, the FBI's planting of an informer in the NAACP and the FBI's running of a secret programme called Cointelpro, created to harass individuals and groups whose policies they did not agree with. The Bureau's programme, for example, attempted to get civil rights leader Martin Luther King, Jr, to commit suicide and secretly broke up marriages of dissidents.

Co-signed by 15 committee members, the letter's lead signatories are Frederick Schwarz, Jr, the former chief counsel to the Church Committee who is now at the Brennan Center for Justice, and the committee's staff director William Green Miller.

While Snowden urged Obama in September to pardon him based on moral grounds before he leaves office in January, the president recently suggested that he was unlikely to do so since he "hasn't gone before a court".

The committee members note that "as the US relationship with Russia deteriorates, the risk to all interests involved increases".

"Without Snowden, it would have been decades, if ever, until Americans learned what intelligence agencies acting in our name had been up to," they wrote. "We know first hand that lack of disclosure can cause just as many, if not more, harms to the nation than disclosure. When intelligence agencies operate in the dark, they often have gone too far in trampling on the legitimate rights of law-abiding Americans and damaging our reputation internationally."