When President Xi Jinping and US President Barack Obama were about to meet in the California desert resort of Sunnylands in June 2013, the US government had worked hard to paint China as a villain in cyberspace.

The revelation made by former National Security Agency contractor Edward Snowden just days before the shirt-sleeves meeting, however, shocked the world. It showed that whatever other countries had done in cyber-surveillance and spying was really nothing compared to the massive scale of operations by the NSA, often labeled as No Such Agency.

To the rest of the world, Snowden is undoubtedly a whistleblower and a great hero because he revealed the US government secret scheme to spy on people all over the world, including foreign leaders who are US allies.

Such spying, which violates people's privacy and civil rights, often involves willing and unwilling collaboration with several major US tech companies.

In the US, debate about whether Snowden is a hero, patriot or traitor is still a divisive issue, despite that his revelation has resulted in the US government and Congress correcting many mistakes.

For example, the panel appointed by Obama to review NSA surveillance programs made dozens of reform recommendations. A federal appeals court has found NSA's call-tracking program revealed by Snowden illegal. The USA Freedom Act passed by the US Congress ended the bulk collection of phone data by the government.

In the past week, Snowden has again been in the spotlight. The German-American movie, Snowden, directed and written by Oliver Stone and Kieran Fitzgerald, hit US theaters on Sept 16.

Meanwhile, Snowden has pleaded for a pardon from Obama, arguing that his massive leak of NSA surveillance programs was "not only morally right" but also "left citizens better off".

On Sept 14, the American Civil Liberties Union (ACLU) Executive Director Anthony Romero called Obama to pardon Snowden by launching the Pardon Snowden campaign that will last untll the end of the Obama administration.

"Thanks to Edward Snowden's act of conscience, we've made historic strides in our fight for surveillance reform and improved cybersecurity," he said.

The ACLU campaign was joined by Amnesty International, Human Rights Watch and a list of more than 100 legal scholars, former national security officials, business leaders, human rights activists and artists.

Romero believes the Espionage Act, which the US government used to charge Snowden, is a World War I era law that doesn't distinguish between selling secrets to foreign governments and giving them to journalists in the public interest.

Most of the people who believe that Snowden is a traitor and should spend the rest of his life in prison argue, as I heard in the latest C-SPAN Journal on Sept 16, that he broke an oath and put the US national security in danger.

It is true that Snowden broke trust, but it occurred in a situation where he found serious wrongdoing by the US government, which is a much more serious crime that people should care about.

Even former US attorney general Eric Holder said that "we can certainly argue about the way in which Snowden did what he did, but I think that he actually performed a public service by raising the debate that we engaged in and by the changes that we made".

However, the US House Intelligence Committee unanimously signed a letter to Obama on Sept 15 not to pardon Snowden, describing his action as causing huge damage to the US intelligence community.

While Obama has commented that the debate triggered by Snowden "will make us stronger", it does not look likely that he will have the guts to pardon Snowden.

Both Republican and Democratic presidential candidates Donald Trump and Hillary Clinton are clearly against a pardon. Trump has repeatedly called for execution of Snowden although he said back in 2013 that he might become a major fan if he could reveal Obama's records.

Contact the writer at [email protected]