Snowden, writing a foreword to 'The Assassination Complex: Inside the Government's Secret Drone Warfare Program' (Simon & Schuster) said that one of the major challenges of being a whistleblower on the US National Security Agency (NSA) is that — once the information is 'out there' — there are still many agents who continue to carry on doing the same.
"They comply in silence, without resistance or complaint. They learn to live not just with untruths but with unnecessary untruths, dangerous untruths, corrosive untruths. It is a double tragedy: What begins as a survival strategy ends with the compromise of the human being it sought to preserve and the diminishing of the democracy meant to justify the sacrifice," he said.
Snowden pointed to the history of whistleblowing, which — although it has exploded in recent years — has still failed to stop government authorities doing what they want, despite legal restrictions and oversight.
As far back as the early 1970s, it was a whistleblower known as 'Deep Throat' who played a crucial role in telling journalists Bob Woodward and Carl Bernstein of The Washington Post about and President Richard Nixon's administration's attempted cover-up of its involvement in a break-in at the Democratic National Committee (DNC) headquarters at the Watergate office complex in Washington, D.C.
In 1971, Daniel Ellsberg — who met Snowden in 2015 — released the Pentagon Papers, while he was working for the RAND Corporation, revealing top-secret decision-making over the Vietnam War. Ellsberg was charged under the Espionage Act of 1917 along with other charges of theft and conspiracy, but — due to governmental misconduct and illegal evidence gathering — his defending lawyers had him acquitted in 1973.
WikiLeaks published documents supplied by US soldier Chelsea (then Bradley) Manning exposing the Afghanistan war logs, the Iraq war logs, a quarter of a million diplomatic cables and the Guantánamo files.
In 2013, Snowden himself exposed the extent of mass surveillance being carried out by the NSA and Britain's GCHQ intelligence agency that caused uproar throughout the world, leading to law changes in the US and the UK, as well as calls for transparency and judicial or legislative oversight of spy agencies.
However, Snowden says history shows that the institutions will continue unrestrained.
"Judges […] have gone to great lengths in the post-9/11 period to avoid reviewing the laws or the operations of the executive in the national security context and setting restrictive precedents that, even if entirely proper, would impose limits on government for decades or more. That means the most powerful institution that humanity has ever witnessed has also become the least restrained," he wrote.
He said, ultimately, the whistleblower is still the greatest check on governments.
"The insiders at the highest levels of government have extraordinary capability, extraordinary resources, tremendous access to influence, and a monopoly on violence, but in the final calculus there is but one figure that matters: the individual citizen. And there are more of us than there are of them," he wrote.