Prosecute Edward Snowden, confessed NSA leaker, to the fullest extent of the law; choices must have consequences.

Edward Showden has made the choice to break the law. He believes that choice was necessitated by the protection of the public good. He may well be right; however, making that choice and then seeking to avoid the consequences is cowardly and illegal.
If his defense is necessity, that will be proven. But breaking the law but whining that one should not be punished is the act of a child.
The law is what must be tested. His actions may have been a valid beginning to that test, but they are not the end.