Sadly that's not how your legal system works any more. I don't have the link handy but it came up here recently with that environmental activist who just got out of jail for breaking up an illegal auction of land. He thought he'd be fine but when the prosecution found that many of the jurors had received a juror's rights pamphlet out lining the basic foundations of your country like that jurys are supposed to be a social check on the laws and the social conscience they threw a fit and they with the judge 1 by 1 interviewed potential jury members and sent home anyone who wouldn't agree to follow the judges orders and interpretations of the law and just vote to convict on weather or not he broke the law, not weather the law was just or what he did was for a greater good.

And so with a jury stacked against him (some may say against the original spirit of your legal system) he ended up with years in jail. Mean while in the course of trying to redo the auction they of course found that it was illegal and didn't do it.

So he felt he'd saved the land and it was worth a few years of his life.

Snowden faces worse and again probably a fairly stacked jury if it were to ever come to that. Tho they could also just indefinitely detain him nakedly in a micro cell in solitary etc etc etc.