There's an exchange in a A Few Days in Athens where the subject of criminal rehabilitation comes up. Metrodorus (having to mind the memory of the scandalous behavior of his brother Timocrates) takes the position that some crimes are so beyond the pale that the guilty are irredeemable. Epicurus seems to take the position that redemption is always possible, and mercy is to be favored if there's a chance of atonement. Not canon, of course, but not bad.
For myself, I rather like that scene from Robert Bolt's play A Man for All Seasons that Christopher Hitchens was fond of citing in defense of free expression.
It's worth noting that for Epicurus justice existed not naturally but by convention. If men convened in order to criminalize impiety (as of course they generally do, when given half a chance), the teachings of Epicurus would themselves be the act of a reprobate. I'm aware that I haven't really answered your question...