  Let us take the third objection first. If impersonal values justify having criminal law, we have reason to opt for whichever set of legal rules will realise those values most efficiently. If one set of powers and permissions will achieve more of the value in question at a lower cost, we should—all else being equal—opt for that set. Now compare two sets of rules. One permits state officials and private persons alike to use force to punish criminals. Another withholds the permissions granted to the former from the latter. We have good reason to think that the first set of rules would bring with it significant costs. Private persons are likely to make more mistakes about who committed crimes, and about how much punishment is appropriate for criminality. Different private punishers are unlikely to punish similarly placed offenders in similar amounts. And as their actions are less easily subjected to public scrutiny, private persons are less easily compelled to punish for the right reasons—in order to do justice rather than settle scores, get revenge, or maximise their profit margins (Moore 2009a, 42; Edwards forthcoming). Avoiding these costs is a strong reason to opt for the second set of rules. True, that set prevents proportionate punishment being imposed by our imagined moot court. But it is plausible to think that this benefit is outweighed by the aforementioned costs. If it is, those who appeal to impersonal values to justify criminal law can explain why the moot court is not permitted to force us to give up our money.