From very early times gambling was forbidden by canon law. Two of the oldest (41, 42) among the so-called canons of the Apostles forbade games of chance under pain of excommunication to clergy and laity alike. The 79th canon of the Council of Elvira (306) decreed that one of the faithful who had been guilty of gambling might be, on amendment, restored to communion after the lapse of a year.
A homily (the famous "De Aleatoribus") long ascribed by St. Cyprian, but by modern scholars variously attributed to Popes Victor I, Callistus I, and Melchiades, and which undoubtedly is a very early and interesting monument of Christian antiquity, is a vigorous denunciation of gambling. The Fourth Lateran Council (1215), by a decree subsequently inserted in the "Corpus Juris", forbade clerics to play or to be present at games of chance. Some authorities, such as Aubespine, have attempted to explain the severity of the ancient canons against gambling by supposing that idolatry was often connected with it in practice. The pieces that were played with were small-sized idols, or images of the gods, which were invoked by the players for good luck. However, as Benedict XIV remarks, this can hardly be true, as in that case the penalties would have been still more severe.
Profane writers of antiquity are almost as severe in their condemnation of gambling as are the councils of the Christian Church. Tacitus and Ammianus Marcellinus tell us that by gambling men are led into fraud, cheating, lying, perjury, theft, and other enormities; while Peter of Blois says that dice is the mother of perjury, theft, and sacrilege. The old canonists and theologians remark that although the canons generally mention only dice by name, yet under this appellation must be understood all games of chance; and even those that require skill, if they are played for money.
The Council of Trent contented itself with ordering all the ancient canons on the subject to be observed. and in general prescribed that the clergy were to abstain from unlawful games. As Benedict XIV remarks, it was left to the judgment of the bishops to decide what games should be held to be unlawful according to the different circumstances of person, place, and time. St. Charles Borromeo, in the first Synod of Milan, put the Tridentine decree into execution, and drew up a list of games which were forbidden to the clergy, and another list of those that were allowed. Among those which he forbade were not only dicing in various forms, but also games something like our croquet and football. Other particular councils declared that playing at dice and cards was unbecoming and forbidden to clerics, and in general they forbade all games which were unbecoming to the clerical state. Thus, a council held at Bordeaux in 1583 decreed that the clergy were to abstain altogether from playing in public or in private at dice, cards, or any other forbidden and unbecoming game. The council held at Aix in 1585 forbade them to play at cards, dice or any other game of the like kind, and even to look on at the playing of such games. Another, held at Narbonne in 1609, decreed that clerics were not to play at dice, cards, or other unlawful and unbecoming games, especially in public.
There was some doubt as to whether chess was to be considered an unbecoming, and therefore, an unlawful, game for clerics. In the opinion of St. Peter Damian it was certainly unlawful. On one occasion he caught the Bishop of Florence playing chess, to while away the time when on a journey. The bishop tried to defend himself by saying that chess was not dice. The saint, however, refused to admit the distinction, especially as the bishop was playing in public. Scripture, he said, does not make express mention of chess, but it is comprised under the term dice. And Baronius defends the saint's doctrine. Some sciolist, he remarks, may say that St. Peter Damian was under a delusion in classing chess under dice, since chess is not a game of chance but calls for the exercise of much skill and talent. Let that be as it may, he proceeds, priests must at any rate be guided in their conduct by the words of St. Paul, who declared that what is not expedient, what is not edifying, is not allowed. http://www.newadvent.org/cathen/06375b.htm