"The detestable custom of duelling, introduced by the contrivance of the devil, that by the bloody death of the body, he may accomplish the ruin of the soul, shall be utterly exterminated from the Christian world. Any emperor, kings, dukes, princes, marquises, counts, and temporal lords by whatsoever other name entitled, who shall grant a place within their territories for single combat between Christians, shall be thereupon excommunicated, and shall be understood to be deprived of jurisdiction and dominion over any city, castle, or place, in or at which they have permitted the duel to take place, which they hold of the church ; and if those places be held as a fief they shall forthwith escheat to their direct lords.
"As to the persons who have fought, and those who are called their seconds (sponsors), they shall incur the penalty of excommunication, and the confiscation of all their property, and of perpetual infamy, and are to be punished as homicides, according to the sacred canons; and if they have perished in the conflict itself, they shall be for ever deprived of ecclesiastical sepulture. Those also who have given counsel in the ease of a duel, whether for the question of right, or fact, or have in any other way whatever persuaded any one thereunto, as also the spectators thereof, shall be subjected to the bond of excommunication, and of a perpetual malediction ; any privilege soever, or evil custom, though immemorial, notwithstanding."
--The Canons and Decrees of the Sacred and Oecumenical Council of Trent, 25th Session (December 3-4, 1563), ed. and trans. J. Waterworth (London: Dolman, 1848), pp. 274-75.