His passport was revoked the day before he left Hong Kong.[1]. He traveled to Russia on what turned out to be an invalid travel document issued by the Ecuadorian embassy in London [2] (same one that Julian Assange is holed up in).

[1] http://bigstory.ap.org/article/ap-source-nsa-leaker-snowdens...

[2] http://www.theguardian.com/world/2013/jul/02/ecuador-rafael-...