If one is allowed to have a favourite prerogative power, the prerogative of mercy is mine. The prerogative of mercy’s only uses are to lift punishment and to lessen suffering. Who could object to that? Yet this “most amiable prerogative” is often under attack.

The latest critic is Joshua Rozenberg. Responding to President Francois Hollande’s decision to pardon a woman serving a long prison sentence, Rozenberg writes:

“Miscarriages of justice, when they occur, should be put right by the courts. And if the courts get it wrong – on sentencing, for example – then parliament should put them right. But ministers must not usurp the role of the judges. … [Pardons] should be granted sparingly – if at all.”

Rozenberg presents the prerogative of mercy as a bit embarrassing, a reminder perhaps of a time when monarchs meddled openly.

Rozenberg assumes that the prerogative of mercy’s main (only?) legitimate use is to correct injustice, and that there are few, if any, injustices that can’t be put right by judges. From these assumptions, I can see how he gets to the conclusion that the prerogative of mercy ought to be used “sparingly – if at all”. I’m not sure about the first assumption, but I’ll take it as given here. The second assumption – that judges can be relied on to correct injustices – seems far too optimistic to me.

“Legal justice” is what we get by applying legal rules. When someone is wrongfully convicted, for example, there’s probably been a legal injustice. Everyone would agree that judges are pretty good at correcting legal injustices. By correcting legal injustices, judges can also hope to do “true justice”, and so to treat people as they truly deserve to be treated. By reversing a wrongful conviction, a judge will do legal justice and true justice. It’s a win for the law, and a win for justice. Put it like this: judges are good at correcting true injustices that are the result of legal injustices.

Things are different when the flaw lies, not in the application of legal rules, but in the rules themselves. In that case what is legally just is truly unjust. There’s injustice built into the system. Judges are not free to rewrite legal rules whenever it suits them. Their law making powers and interpretive techniques are limited, as they should be. Those limits mean that judges are pretty bad at correcting true injustices that aren’t the result of legal injustices.

If judges can’t replace a flawed law themselves, shouldn’t Parliament come to the rescue? Sometimes, sure; but often, no. That’s because legal rules, like all rules, are blunt by nature. Rules are generalizations about what ought to be done. They’re designed for the usual case, not for each case to which they apply. Rules can be made more precise, at the cost of clarity. Rules can confer case-by-case discretion, at the cost of predictability. But even the best designed rule will be overbroad. Parliament can legislate all it likes, but even the best set of statutes will leave the possibility of injustice.

If there are injustices that neither judges nor Parliament can avoid, that leaves only the executive. And so we arrive back at the prerogative of mercy. One of the prerogative of mercy’s proper uses is to correct for inevitable overbreadth in the law. By using the prerogative to correct for overbreadth, the executive does not stray into judicial territory. On the contrary, the executive fulfils a distinctive and valuable constitutional role. I wish I could present this as an original insight, but in fact “individuation in the criminal law” has been an established part of mercy “since at least the eleventh century”, as Carla Ann Hage Johnson describes.

Although the prerogative of mercy is still valuable, it has its dangers. If the prerogative of mercy were to be used too often, legal rules would become an unreliable guide to legal consequences. That would undermine the rule of law. We’re far from this point, however. The bigger concern is that the prerogative will be used, not to correct for legal overbreadth, but to repay political favours or for other bad reasons (a possibility that Rozenberg worries about, too).

Re-enter the judges. Mercy used to be an “act of grace”, as the Privy Council said in Reckley v Minister of Public Safety and Immigration (No 2). It was free from legal constraint. That’s changing, however. There’s now limited judicial review of mercy decisions in the UK, and other Commonwealth jurisdictions have gone much further. Judicial review in this area carries its own risks (e.g. by making it rule-like), but it has the potential to avoid the worst abuses by the executive. There might be circumstances in which, for example, judges should be willing to review a refusal of mercy that is the result of bad faith.

So the executive and judges have complementary roles. In their sentencing capacity judges should do justice according to law. The executive should sometimes use the prerogative of mercy to mitigate the law’s overbreadth, thereby doing true justice. And on the margins, judges may have a role to play in limiting abuses of the prerogative of mercy.  But it would be a shame if a misconception about the separation of powers were to lead to the prerogative’s atrophy through underuse.  We need more mercy not less.

Adam Perry 
Associate Professor in the Faculty of Law and Garrick Tutor and Fellow at Brasenose College
University of Oxford