Capital Punishment(source - punctuation and citation as in original, footnotes omitted)
2266 The State's effort to contain the spread of behaviors injurious to human rights and the fundamental rules of civil coexistence corresponds to the requirement of watching over the common good. Legitimate public authority has the right and duty to inflict penalties commensurate with the gravity of the crime. the primary scope of the penalty is to redress the disorder caused by the offense. When his punishment is voluntarily accepted by the offender, it takes on the value of expiation. Moreover, punishment, in addition to preserving public order and the safety of persons, has a medicinal scope: as far as possible it should contribute to the correction of the offender.
2267 The traditional teaching of the Church does not exclude, presupposing full ascertainment of the identity and responsibility of the offender, recourse to the death penalty, when this is the only practicable way to defend the lives of human beings effectively against the aggressor.
"If, instead, bloodless means are sufficient to defend against the aggressor and to protect the safety of persons, public authority should limit itself to such means, because they better correspond to the concrete conditions of the common good and are more in conformity to the dignity of the human person.
"Today, in fact, given the means at the State's disposal to effectively repress crime by rendering inoffensive the one who has committed it, without depriving him definitively of the possibility of redeeming himself, cases of absolute necessity for suppression of the offender 'today ... are very rare, if not practically non-existent.'[John Paul II, Evangelium vitae 56.]
Many folks will recall that Rome was not traditionally opposed to the death penalty, particularly for accused heretics. However, Rome's view on this moral issue has been shifting to the liberal end of the spectrum, as evidenced by the CCC items above, which make capital punishment justifiable only in "very rare" if not "practically non-existent" circumstances.
Of course, the laws of Vatican City were originally drafted in older days, when this modernist mentality had not yet carried the day. Thus, the constitution of the Vatican City provided for capital punishment. However, it now reported that finally the laws of Vatican City have caught up to the shift in Rome's view of morality (link to report). Thus, the Vatican City will join the ranks of other nations who are unable to obey the following commands:
Exodus 22:18 Thou shalt not suffer a witch to live.
Genesis 9:6 Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man.