The next day, a secret court in Virginia ordered the owner of a small email provider in Texas to help investigators surveil Snowden's email communications.

That order set off a long legal fight that was mostly shrouded in complete secrecy for two months, until Ladar Levison, the owner of the email provider called Lavabit, decided to shut down his service rather than "become complicit in crimes against the American people," as he put it at the time.

Even then, most details of the case remained under seal until October 2013, when a judge in Alexandria agreed to publish part of the court documents filed in the fight. Finally, in early March of this year, almost three years later, the judge ordered even more documents to be released.

Some information in the court documents still remains redacted, such as the basis, or "probable cause," as to why the US government was interested in Snowden's email data.