Snowden was sued for theft of government property and violation of section 793(d) and 798(a)(3) of the ESPIONAGE ACT.
The crime under these sections carry possible sentence of 30 years imprisonment. He can not be charged the crime of TREASON since it(treason) requires individual(s) waging war against the United States or a act of aiding United States' enemies.
The word 'Espionage' means the practice of spying to get information about the activities of foreign government(s).
Section 798(a)(3) forbids intentionally communication of confidential files to an unauthorized individual(s). The United States Supreme Court recognize the fact that employees of the government working with National security are in a POSITION OF TRUST that LIMITS THEIR FIRST AMENDMENT RIGHT to DISCLOSE INFORMATION.
