Or even when the answer is going to be yes? Snowden shouldn't need a pardon for what he's done. Any federal prosecutor that would even consider laying charges should be removed from office immediately.
The laws he broke being immoral/unconstitutional/for the greater good is to be determined by the judge/jury, not the prosecutor.
A presidential pardon solves Snowdens issue, but does not change the law.
Justice is for the courts to decide, not the prosecutor. But whether enforcing a law serves to uphold the public order is up to the prosecutor. And enforcing bullshit laws is just as problematic as being inconsistent in what laws you do enforce.
It's not up to the prosecutor to determine whether or not a law is just or not. That is not his job, that is a job for the judge/jury.