Is someone really "guilty" of breaking an unjust law?
No.
An unjust law is no law at all
Agreed. So, in this case, a "pardon", now that I think about it, isn't exactly the right thing, in a sense. I mean, it's a nice token gesture, but it still implies that a law was actually broken. An apology for being victimized by a non-law would be more appropriate.