Edward Snowden is simply a whistle-blower, exposing unconstitutional privacy infringement abuses by the US Federal government against its own citizens. Full Stop.
The outdated Espionage Act was not designed for nor could its spirit predict its use for this purpose. As the former Attorney General stated 'Snowden performed a public service...'. Drop the charade and the charges; admit wrongdoing and allow Snowden to come back home unmolested.