Actual guilt necessary for punishment
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Punishment of innocents is against the law of nature because punishment is only for transgression of the law.
All punishments of innocent subjects, be they great or little, are against the law of nature: for punishment is only for transgression of the law, and therefore there can be no punishment of the innocent. It is therefore a violation, first, of that law of nature which forbiddeth all men, in their revenges, to look at anything but some future good: for there can arrive no good to the Commonwealth by punishing the innocent. Secondly, of that which forbiddeth ingratitude: for seeing all sovereign power is originally given by the consent of every one of the subjects, to the end they should as long as they are obedient be protected thereby, the punishment of the innocent is a rendering of evil for good. And thirdly, of the law that commandeth equity; that is to say, an equal distribution of justice, which in punishing the innocent is not observed.
Hobbes, Lev XXVIII 22
Proposition and illustration
It is against the law of nature to punish the innocent.
...For example sake, it is against the law of nature to punish the innocent; and innocent is he that acquitteth himself judicially and is acknowledged for innocent by the judge. Put the case now that a man is accused of a capital crime, and seeing the power and malice of some enemy, and the frequent corruption and partiality of judges, runneth away for fear of the event, and afterwards is taken and brought to a legal trial, and maketh it sufficiently appear he was not guilty of the crime, and being thereof acquitted is nevertheless condemned to lose his goods; this is a manifest condemnation of the innocent. I say therefore that there is no place in the world where this can be an interpretation of a law of nature, or be made a law by the sentences of precedent judges that had done the same....
Hobbes, Lev XXVI 24