There are canon laws of ecumenical councils, of provincial and local councils, and of individual church fathers which have been received by the entire Orthodox Church as normative for Christian doctrine and practice. As a word canon means literally rule or norm or measure of judging. In this sense the canon laws are not positive laws in the juridical sense and cannot be easily identified with laws as understood and operative in human jurisprudence.
The canons of the Church are distinguished first between those of a dogmatic or doctrinal nature and those of a practical, ethical, or structural character. They are then further distinguished between those which may be changed and altered and those which are unchangeable and may not be altered under any conditions.
The dogmatic canons are those council definitions which speak about an article of the Christian faith; for example, the nature and person of Jesus Christ. Although such canons may be explained and developed in new and different words, particularly as the Church Tradition grows and moves through time, their essential meaning remains eternal and unchanging.
Some canons of a moral and ethical character also belong to those which cannot be changed. These are the moral canons whose meaning is absolute and eternal and whose violation can in no way be justified. The canons which forbid the sale of Church sacraments are of this kind.
There are, in addition, canons of a quite practical nature which may be changed and which, in fact, have been changed in the course of the life of the Church. There are also those which may be changed but which remain in force since the Church has shown the desire to retain them. An example of the former type is the canon which requires the priests of the church to be ordained to office only after reaching thirty years of age. It might be said that although this type of canon remains normative and does set a certain ideal which theoretically may still be of value, the needs of the Church have led to its violation in actual life. The canon which requires that the bishops of the Church be unmarried is of the latter type.
It is not always clear which canons express essential marks of Christian life and which do not. There are often periods of controversy over certain canons as to their applicability in given times and conditions. These factors, however, should not lead the members of the Church to dismay or to the temptation either to enforce all canons blindly with identical force and value or to dismiss all the canons as meaningless and insignificant.
In the first place, the canons are "of the Church" and therefore cannot possibly be understood as "positive laws" in a juridical sense; secondly, the canons are certainly not exhaustive, and do not cover every possible aspect of Church faith and life; thirdly, the canons were produced for the most part in response to some particular dogmatic or moral question or deviation in the Church life and so usually bear the marks of some particular controversy in history which has conditioned not merely their particular formulation, but indeed their very existence.
Taken by themselves, the canon laws of the Church can be misleading and frustrating, and therefore superficial people will say "either enforce them all or discard them completely." But taken as a whole within the wholeness of Orthodox life -- theological, historical, canonical, and spiritual --- these canons do assume their proper place and purpose and show themselves to be a rich source for discovering the living Truth of God in the Church. In viewing the canons of the Church, the key factors are Christian knowledge and wisdom which are borne from technical study and spiritual depth. There is no other "key" to their usage; and any other way would be according to the Orthodox faith both unorthodox and unchristian.
CANON LAW: the term "canon" is a Greek word that comes from Hebrew and means a "reed or straight rod" used in measuring, i.e., a "yardstick" which has the same bivalent senses in English). In early Christianity it was used to connote a rule or norm of behavior, truth, or faith (Gal 6:16). Canons are distinguished from dogmas (q.v.) in that canons are generally disciplinary rules for the organization and administration of the Church, whereas, dogmas are immutable doctrines and basic principles of faith. For example, canons may be changed by human agency but dogmas may not. The canons of the seven ecumenical councils (q.v.) are given certain precedence in the Eastern Church over laws of local churches.
Canons differ also from state laws on Church matters, an important point since Orthodoxy has a long history of relations between Church and state (q.v.). Every state defines the relationship between itself and Church bodies, but this is not Canon Law. Canon Law differs both in origin and discipline from state law, e.g., Byzantine Law (q.v.). Canon Law is made by the Church, while state law is issued by secular powers - two different institutions of society. Further, the principle of the Church discipline is voluntary obedience and not forced constraints, as it is with the state. It is true that the Church may impose disciplinary punishment for violation of Canon Law, but these disciplinary measures are to be voluntarily accepted and followed: they are not forced. The most severe ecclesiastical discipline is excommuication, which in itself might not even physically separate the individual from the community. In summary, Canon Law is passed by the Church itself and established by its own legislative bodies. Church law does not lose its specific character if, as sometimes happens, the state assumes responsibility for it and approves it. Ultimately, the Church is responsible for the formation and application or "economy" (q.v.) of its own laws.
Eastern Orthodox Canon Law comes from three sources: Holy Scripture, Church legislation, and Church custom. Although the Scriptures (q.v.) are the basic source of Canon Law, one would search in vain there for a detailed system of Church organization. The significance of Scripture as it relates to Canon Law is that it embodies principles of Christian doctrine from which rules may be extrapolated for solving disciplinary problems within the Church - but only the Church itself may do that. The second source, Church legislation, originated not only as written rules, but also as oral tradition. The legislation is comprised of local Church councils preceding the Ecumenical Councils, the Ecumenical Councils themselves, and the local Church councils afterwards. Church custom or usage is different from Holy Tradition (q.v.) in that Holy Tradition is looked to for dogma, while custom is a source for ecclesiastical discipline. For example, Basil of Caesarea (q.v.) emphasized repeatly that some disciplinary rules were accepted "not on the ground of any Canon but only on the ground of useage followed by those who have preceded us" (Canon 4, 87). Still, not every custom may be a basis of Canon Law. In order to be so, the custom must have been observed for a long time, it must have been freely subscribed to, and it must be in conformity with the principles of faith and order.
The body of Canon Law of the early Church, included the Apostolic Canons, the Canons, of the Ecumenical Councils, the Canons of the Local Councils, and the Canons of the Holy Fathers. Later collections that were popularly used are those of Dionysius Exiguus, John Scholasticus, Syntagma Canonicon, The Nomocanons, and the 12th century Canonical Editions of Aristenus, Zonaras, and Balsamon (qq.v). The most extensive, comprehensive collection in modern times were made by Russian, Greek, Serbian, and Bulgarian scholars of the 19th century. The best available English edition of the canons of the undivided Church is H. R. Percival's volume XIV of the Library of Nicene and Post-Nicene Fathers.
From: Historical Dictionary of the Orthodox Church – by Michael Prokurat, Alexander Golitzin and Michael D. Peterson