The law the Obama administration wants to use to prosecute him takes no account of whether revealing this information was a public service. Under the antiquated Espionage Act of 1917, the only issue is whether “national defense” information was given to someone not authorized to receive it. It doesn’t matter if the secrets revealed wrongdoing or if they endangered the national defense, whether they were passed to an American journalist or to a foreign enemy.

There is obviously a public interest in enabling the government to keep some national security information secret. But under international human rights law, the public interest — not any particular government’s interest — is crucial. The protection of national security and public order may provide legitimate reasons for not disclosing certain sensitive information, but suppressing embarrassing or disturbing news does not. No one should be prosecuted for exposing human rights violations. At the very least, there has to be a genuine opportunity to offer a public interest defense.

The enormous value of Mr. Snowden’s revelations is clear. What was their harm? Scant evidence has been provided for many officials’ ominous statements. Some officials have warned that the terrorism-related activity of certain groups has become harder to monitor, but the most dangerous adversaries have always taken precautions against surveillance, with at least one independent study showing little impact from the Snowden revelations.