"Our beliefs dictate that justice be served but mercy be shown," Scottish Justice Secretary Kenny MacAskill said. He added that Megrahi "now faces a sentence imposed by a higher power. . . . It is terminal, final and irrevocable. He is going to die." (source)
It's interesting because it identifies the role of mercy between human beings, even for those who have committed terrible crimes or inflicted evils on the world. Mercy is not often granted to people like Megrahi.
Machiavelli had an opinion on mercy that applies here, insisting that it should only come after the willingness and capacity to punish had already been well established. In this case, MacAskill has been quite Machiavellian. Megrahi was sentenced and served much of that sentence, thus giving value to the mercy (according to Machiavelli).
This view of mercy, that it should only exist in contrast to a history of actual punishment, is not dissimilar to the idea of the mercy for Christians at a Final Judgement. However, as the core of that idea is the insistence that God has punished, continues to punish, and will continue to punish according to divine will. This Machiavellian God fits the model of God-as-earthly-monarch. The model collapses when God is not viewed as a kind of earthly monarch, but when God defines what it means to be a divine monarch.
The power of conquest and legislation is not the power of God because God's power is shown in weakness. Weakness is powerful because it cuts across the natural order to exert power and assert self-interest. Weakness (so-called) is only weak because it denies any claim to assertion of power. In fact, it is powerful because it can act without fear of consequence from the natural order. Thus, this kind of mercy does not need the merciful person to have previously demonstrated punishment. Rather, it requires that the merciful person gives up any claim to administer punishment.
The criticism will come, no doubt, that this will make for a terrible system of government. That's true. A government needs laws to guarantee the perpetuation of society. However, this idea of mercy is meant for those who eschew the primacy of government, for those who follow God-as-divine-monarch, who will live in weakness.