“They,” obviously, are the unrepentant souls standing before Yahweh for judgment. For them, it “shall be as though there had been no redemption made”; they are in the same condition as if Messiah had never atoned for them. Alma separates the atonement into two separate aspects, the atonement for death and the atonement for sin. This argument depends upon the Messiah’s completion of the atonement for death, resulting in the individual’s resurrection, but the individual’s personal denial of the atonement, resulting in a refusal to repent.
“… for they cannot be redeemed according to God’s justice;… ”: In fact, it is impossible for God to redeem such individuals. Redemption from sin is conditional, and the person has not met the conditions. This is not God’s choice; it is the choice of the unrepentant individual. Having rejected God’s grace that provided for redemption from sin, the person now has no other recourse. Not even the all-powerful God can help him, for God is just and justice requires that the law be applied.
“… and they cannot die,… ”: Because this individual has been resurrected, he or she cannot die again and therefore will have no second opportunity to stand before another judgment bar.
Reference: “… seeing there is no more corruption.”: This phrase draws on 1 Corinthians 15:42–50. “Corruption” means mortality. This statement might be rephrased as “seeing there is no more mortality.” Since mortal life is over and the resurrection has supplied a body that will not die, the person is condemned forever with no means of changing his or her fate.