Pastoralis Officii §1

¹ Mindful of your pastoral duty and moved by your love of neighbor, you wrote to me last year concerning the frequent practice among your people of a private, individual contest called dueling. You indicate, not without grief, that even Catholics customarily engage in this type of combat. At the same time your request that We, too, attempt to dissuade men from this manner of error. It is indeed a deadly error and not restricted to your country, but has spread so far that practically no people can be found free from the contagion of the evil. Hence, We praise your zeal. It is clearly known what Christian philosophy, certainly in agreement with natural reason, prescribes in this matter; nevertheless, because the vicious custom of dueling is being encouraged with greatest forgetfulness of Christian precepts, it will be expedient to briefly review these rules.