Canon Law (jus canonicum) is, strictly speaking, that part only of ecclesiastical legislation in and by synods of spiritual persons which is concerned with the moral and disciplinary government of the Christian church, and is embodied in the form of canons or rules. It is thus distinct alike from the dogmatic decisions of similar synods, embodied in decrees, affecting formularies and standards of doctrine; from papal law (jus pontificium); and from enactments of the civil power upon ecclesiastical subjects (jus ecclesiasticum), though the last often overlaps the canon law proper. The earliest example of the enactment of such laws is in Acts, xv. 6-29, when the council of apostles and elders at Jerusalem framed rules of discipline for the new Gentile converts. It was not until the conversion of the empire, however, that it was feasible for canons of synods to have more than local currency and merely consensual force. From that time two new factors enter into the evolution of canon law—the general councils, which either themselves enact canons to bind all Christendom, or give their sanction to those enacted by local synods, thereby similarly extending their scope; and the sanction of the civil power, validating church canons so as to give them legal force and coercive authority.
Canon Law is broadly divided into Eastern and Western. The canon law of the Eastern Church is a comparatively brief code, composed exclusively of few, homogeneous, ancient, and authentic materials, and has remained unaffected by change or accretion for a thousand years. It consists of the following matters: (1) The disciplinary canons of the seven councils recognised as oecumenical by the Greco-Russian Church—namely, Nice I., Constantinople I., Ephesus, Chalcedon, Constantinople II. and III., Quinisext in Trullo (accounted by the Easterns as supplementary to the fifth and sixth oecumenical councils, and therefore not separately reckoned), and Nice II.; (2) the ancient code of laws known as 'Apostolical Canons'; (3) the canons of various lesser synods, Eastern and African, accepted and sanctioned by one or other of the greater synods; (4) canons promulgated by Dionysius and Peter of Alexandria, Gregory Thaumaturgus, Athanasius, Basil the Great, Gregory of Nyssa, Theophilus and Cyril of Alexandria, and canonical epistles of Gennadius and Tarasius of Constantinople; (5) the comments and glosses thereupon of the 12th-century canonists Theodore Balsamon, Joannes Zonaras, and Alexius Aristenus, which, though not properly part of the body of law, have been usually treated as authoritative interpretations. The earliest attempt at codifying the Eastern laws (there were various partial collections made previously) was the Syntagma Canonum or Nomocanon, compiled in the 6th century by John the Scholastic; the final one was the Nomocanon of Photius, patriarch of Constantinople, compiled about 880 A.D. All the main documents of this Eastern code are to be found in the Synodikon or Pandectæ of Bishop Beveridge (2 vols. folio, Oxford, 1672-82). The civil validation of the Eastern canon law was first effected by Novel cxxxi. of the emperor Justinian.
The Western canon law is of much greater extent, is composed of much more diversified materials, inclusive of a large element of papal law, and has undergone continual changes by means of successive accretions and interpolations, many of the latter being spurious, besides being further complicated by the codes of canons enacted by national churches, and having local currency only, but co-ordinate with the main Latin code in the several territories within which they are or were in use.
The earliest full collection of canons received in the West was made almost contemporaneously with the earliest Eastern one, and is due to Dionysius Exiguus, a Scythian monk of the 6th century, who translated the Greek portion of his materials into Latin, and issued (circa 550 A.D.) the whole in a body of 401 canons, being those of the Apostles, Nice I., Ancyra, Neocæsarea, Gangra, Antioch, Laodicea, Constantinople I., and Chalcedon, the so-called canons of Sardica, and the African code of 138 canons. To these he added further all the decretal epistles of popes with which he was acquainted, beginning with Siricius in 385, and ending with Anastasius II. in 496, thus discrediting in advance the long subsequent forgery of the False Decretals, which professedly went back much earlier. This collection was adopted at Rome, and received there its first accretions in the decretals of popes later than the time of Dionysius, down to Gregory II. (715-31). It was this co-ordination of papal epistles and rescripts with the canons of councils, as holding equal rank and authority, which was the distinguishing feature of the compilation by Dionysius, thus winning it that acceptance at Rome which was never accorded to the nearly simultaneous Breviatio Canonum by Ferrandus of Carthage (547). In its augmented shape, the Dionysian collection was formally recognised as the canon law of the Roman Church, and not merely was tacitly received as such in Western Europe and in Africa, but was sent officially by Pope Hadrian I. to Charlemagne, and solemnly received by the great synod of Aix-la-Chapelle in 803, whence it bore for a time the name of Codex Hadrianus. It was similarly recommended to the English bishops by Leo IV. about forty years later. Its fortunes in Spain were even more noticeable and momentous. Adopted there by (or at least in the time of) Isidore of Seville, and published under his name, it speedily supplanted an earlier collection by Martin of Braga, and prepared the way for the great forgery known as the False Decretals, possibly fabricated in Western Gaul, but published in Spain about 845 by Isidore Mercator, and easily passing, through the coincidence of editorial name, into the earlier and genuine Isidorian code. These false decretals consist of about one hundred spurious documents, inclusive of alleged papal rescripts, from Clement I. in the 1st century, to Sylvester in the 4th, and containing also the pretended Donation of Constantine. Nicolas I., then pope, saw how advantageous to himself this testimony must prove, and hastened to give it recognition, causing it to be embodied in the body of Roman canon law, wherein (despite the universal modern admission of its spuriousness) it continues to form a large and influential factor. The simple fact that search in the Roman archives must at once have established the non-existence of the whole collection, brands Nicolas with acting in conscious bad faith, whereas it is possible that the other persons then concerned in giving circulation to it may have been more or less honestly deceived.
The next important stage in the evolution of the canon law was the Decretum of Burchard of Worms in 1025, after which came the collections of Anselm of Lucca and Cardinal Deusdedit, about 1086, much increasing the papal factor. Soon followed the collection made by Ivo, Bishop of Chartres, about 1114. He seems to have taken the earlier work of Burchard of Worms, largely citing the False Decretals, and long current in Germany, as his model and guide, for his Decretum follows its method closely, and often adopts its very words. All these collections, however, had one common defect as legal codes. The canons they contained, passed by councils widely apart in time, place, and circumstances, were often conflicting and contradictory, and thus perplexing rather than instructing those who consulted them for practical guidance. To meet this difficulty, Gratian, a Benedictine monk of Italian birth, and professed in a monastery at Bologna, compiled, between 1139 and 1142, a Concordia discordantium Canonum, published at Rome in 1144, for the purpose of showing how the opposing provisions could be reconciled; and this work (commonly cited as the Decretum Gratiani) met with immediate success, and exercised a powerful influence on the interpretation of the canon law. He appears to have taken the idea from the Pandects of Justinian, then recently discovered, and brought his collection down from the time of Constantine the Great to the pontificate of his contemporary, Pope Eugenius III., who approved it, and is alleged (but on insufficient evidence) to have at once licensed it to be read in the law-schools, and accepted as authoritative. Whether it obtained this special sanction or not, at any rate it did make its way into the law-schools, and enjoyed a dominating influence therein. It included the False Decretals, and no fewer than 367 spurious canons, and thus powerfully contributed to the falsification of the Western code. To this period belongs the term 'Jus Canonicum' itself, not found earlier, and having no Greek equivalent. A further collection of the growing mass of fresh decretals needed to be made, and this was first undertaken by Bernardo Circa, Bishop of Faenza, who brought them down to the pontificate of Celestine III. (1191-98). But this collection was superseded by that formed at the instance of Pope Gregory IX. by his chaplain, Raymond de Pennaforte (afterwards general of the Dominicans, and canonised), about the year 1234. This body of documents forms that portion of the Corpus Juris Canonici entitled Decretales Gregorii Papæ IX., comprised in five books. To these were added a sixth by Boniface VIII. in 1298, known as Scxtus Decretalium, or more briefly, the Sext. The next addition was the Clementina, or constitutions promulged by Pope Clement V. at the Council of Vienne in 1308, and republished by his successor, John XXII., in 1317, who subjoined thereto twenty fresh enactments of his own entitled Extravagantes Joannis. Five books of still more recent documents, named Extravagantes Communes, coming down to 1483, in the pontificate of Sixtus IV., have further been embodied in the code; and the whole of these materials are collectively styled Corpus Juris Canonici, of which a corrected and standard edition was published by order of Pope Gregory XIII. But the word 'corrected' does not denote rejection of the spurious factors. The False Decretals, though called in question even before the Reformation by Nicolas of Cusa (1401-64) and Cardinal Torquemada (1388-1468), powerfully controverted by the Magdeburg Continuators in the Reformation era itself (1560-74), and finally discredited by David Blondel in his Pseudo-Isidorus et Turrianus Vapulantes (Geneva, 1628), still constitute, as already said, an important element of the contents.
This code, however, as already implied, is, properly speaking, that of the local Roman Church and its immediate dependencies alone. All other parts of Western Europe had their local canon law derived from national synods and similar sources. Thus, in the empire, the Capitularies of Charlemagne and his successors contributed largely to the ecclesiastical law of Germany; and several collections of these (analogous to the Italian collec- tions of papal decretals) were made from time to time, beginning with that of Angesisus, Abbot of Fontenelle, in 827, recast and much enlarged by Benedict of Mainz twenty years later; and a collection passing under the name of Angilram or Ingelram, Archbishop of Metz, Charlemagne's chaplain and almoner, is noticeable as containing large extracts from the False Decretals, and as being hyper-papal in tone, whence it has been conjectured to have been the first draft of the more extensive forgery of Isidore Mercator, and probably also from his pen. In France a great body of canon law, framed independently of Rome, was compiled from the enactments of a long series of national synods, and helped to build up those Gallican liberties which were steadily maintained against attempted papal encroachments. Spain, too, though more readily admitting papal intervention, had its peculiar local code. In England, partly from national character, and partly by reason of its remoteness from Italy, the growth of a national code of canon law was rapid and luxuriant. Most of the enactments of which it consists were framed in provincial synods under various archbishops of Canterbury; but a certain proportion is formed of Legatine Constitutions, enacted in synods held under the papal legates, Otho and Othobon, sent to England by popes Gregory IX. and Clement IV. in the reign of King Henry III., and between the years 1220 and 1268. At the era of the Reformation, the statute for the submission of the clergy and restraint of appeals (25 Henry VIII. chap. 19) enacted that a commission of thirty-two persons, half clergy and half members of the two houses of parliament, should review and report on the existing canons; such as the commission approved were to be revalidated by the king's assent under the great seal, and such as they disallowed to be abolished. In the meantime, all such existing canons as were not contrariant to the laws of the realm, nor hurtful to the king's prerogative, should still be used and executed. But this commission never met nor acted, and attempts to bring it into operation fell through under both Edward VI. and Elizabeth, and have not since been renewed. The legal result is that the statute of Henry VIII. remains the ruling one upon the subject, and thus that all the ancient canon law of England, which does not conflict with former or later canons or civil statutes, is still binding in ecclesiastical law. For post-Reformation canons, see CANONS OF THE CHURCH OF ENGLAND.
The bibliography of the canon law is very extensive, and only a few of the most essential works can be given here: Beveridge, Synodikon, sive Pandectæ Canonum (2 vols. folio, Oxford, 1672-82), and Collatio Synodici (2 vols. folio, Oxford, 1677); Justellus, Bibliotheca Juris Canonici Veteris (2 vols. folio, Paris, 1661); Fleury, Institution au Droit Ecclésiastique (2 vols. 12mo, Paris, 1771); Maastricht, Historia Juris Ecclesiastici (8vo, Halle, 1719); Corpus Juris Canonici, edd., Friedberg et Richter (2 vols. 4to, Leip. 1879); C. J. Vidmar, Introductio ad Corpus Juris Utrius. (Vienna, 1886); Böhm, Jus Eccl. Protest. (Halle, 5 vols. 1730); De Marca, De Concordia Sacerdotii et Imperii (folio, Paris, 1663); Van Espen, Jus Ecclesiasticum Universum (5 vols. folio, Cologne, 1777); Ferraris, Prompta Bibliotheca Canonica (8 vols. 4to, The Hague, 1781); Lyndwood, Provinciale, sive Constitutiones Anglicæ (Oxford, folio, 1679); Ayliffe, Parergon Juris Canonici Anglicani (folio, Lond. 1726); Johnson, Collection of the Laws and Canons of the Church of England (2 vols. 8vo, Oxford, 1851); Gibson, Codex Juris Ecclesiastici Anglicani (2 vols. folio, Oxford, 1761).