This excellent article from Crisis Magazine explores the issue further.

The classic statement about it is from Romano Amerio and can be found here.

An excerpt from the Crisis Magazine article.

“This piece on capital punishment is a revision of the original, which first appeared in Latin Mass Magazine (Summer 2001). It is written from a “traditionalist” perspective, a traditionalist being simply a Catholic who affirms—as a Catholic must—that the Second Vatican Council changed nothing of what a Catholic must believe in order to be a member of the Church in good standing. As the First Vatican Council declared: “For the Holy Spirit was not promised to the Successors of Peter that by His revelation they might disclose new doctrine, but that by His help they might guard the revelation transmitted through the apostles and the deposit of faith, and might faithfully set it forth.” (Cf. Denzinger, §1836)

“Of course, an authentic development of doctrine is always possible in the sense of a fuller explication of what the Church has always taught.  But neither a Pope nor a Council has an oracular function of providing the latest and most reliable Catholic teaching. The Catholic faith, unlike the statute books on which lawyers rely, does not involve periodic “pocket parts” containing amendments or repeals to be inserted into the back of the book.  If the “hermeneutic of continuity” means anything, it means that Catholic teaching on faith and morals is not subject to reversal. A reversible Magisterium would be no Magisterium at all, but rather a human agency bereft of the promises of Christ—like the Protestant sects which have abandoned doctrine after doctrine over the centuries since Luther began the process of abandonment.

“The Traditional Teaching on Capital Punishment

“And so it is with Catholic teaching on the morality of capital punishment. According to the constant teaching of the Church, God Himself has ordained that legitimate civil authority shall have the right and duty to punish deliberate murder (and other grave crimes) with the penalty of death. Capital punishment honors the Fifth commandment, because it vindicates the sanctity of human life. Hence, in its teaching on the Fifth Commandment the Catechism of the Council of Trent declares:

“Again, this prohibition does not apply to the civil magistrate, to whom is entrusted the power of life and death, by the legal and judicious exercise of which he punishes the guilty and protects the innocent. The use of the civil sword, when wielded by the hand of justice, far from involving the crime of murder, is an act of paramount obedience to this commandment which prohibits murder. The end of the commandment is the preservation and sanctity of human life, and to the attainment of this end, the punishments inflicted by the civil magistrate, who is the legitimate avenger of crime, naturally tend, giving security to life by repressing outrage and violence.”

“As the Tridentine Catechism teaches, the death penalty protects the sanctity of life through legitimate legal vengeance to repress outrage and violence in society. This involves just retribution and deterrence as legitimate aims of penal law.

“The Catechism’s reference to the civil sword evokes St. Paul’s teaching on the divine right of civil authority to avenge wrongdoing by the sword: “But if thou do that which is evil, fear: for he beareth not the sword in vain. For he is God’s minister: an avenger to execute wrath upon him that doeth evil.” Rom. 13:4 Reflecting on this passage, St. Thomas teaches that capital punishment imitates divine justice; for after all, eternal damnation is the ultimate form of capital punishment: “According to the order of His wisdom God sometimes slays sinners forthwith in order to deliver the good, whereas he sometimes allows them time to repent, according as what is expedient to His elect. This also does human justice imitate according to its powers . . .” (ST II-II, Q. 64, Art. 2)

“Thus the right of civil authority to punish evildoers by the sword in appropriate cases is a matter of revealed truth, not a changeable prudential judgment.  This is not to deny that civil authority can exercise prudential judgment in abstaining from the exercise of its right to impose capital punishment, or even abolish it entirely in keeping with historical circumstances.  For example, earlier this year the Governor of Illinois, Pat Quinn, signed an executive ban on the death penalty in his state given the appalling evidence of numerous executions of innocent persons in Illinois based on “forced confessions, unreliable witnesses, and incompetent legal representation.” As a lawyer, I am well familiar with the grave potential in any legal system for catastrophic miscarriages of justice which, in the case of capital punishment, cannot be rectified. The Church has never taught that civil authority must impose capital punishment for murder, but only that it has a divine sanction when it does so.”