Full Idea
All murderers …must suffer the death penalty. This is what justice, as the idea of judicial power, wills in accordance with universal laws of a priori origin.
Gist of Idea
Justice asserts the death penalty for murder, from a priori laws
Source
Immanuel Kant (Metaphysics of Morals I: Doctrine of Right [1797], §49 Gen E)
Book Reference
Kant,Immanuel: 'Political Writings', ed/tr. Reiss,Hans [CUP 1996], p.157
A Reaction
Illustration of how giving a principle an a priori origin puts it beyond dispute. Kant is adamant that mercy mustn't interfere with the enactment of justice. And Kant obviously rejects any consequentialist approach. Remind me what is wrong with murder?