This might help.  I admit to robbing a bank in Idaho in 1926.  I was never charged or sentenced for this.  I left the United States to then joined the Nazi party and served in the German Army in WWII as a prison guard in Poland where Jews were exterminated in gas chambers. I then went to live in Argentina under a fictitious name.  I have no valid United States passport.  May I have a pardon from the United States government.  Ridiculous.  Outlandish but in Snowden's case he admits to stealing secrets, never being caught or tried, leaving the country and now his passport has be revoked.  Snowden need to be found guilty of something in the United States, sentence, to receive a pardon.  He has informally chosen to a self imposed exile.  He fight is to regain his passport.