Canon law is the legal system of the Roman Catholic Church, i.e. the normative principles whereby the Church and its members are governed, in terms of the Church's areas of secular and spiritual authority.
In the New Testament and in early church writings, the term "canon" is used to mean any guide to proper Christian living. Later, the word came to be applied to Church statutes that must be obeyed; or, alternately, the whole system of Church law and jurisprudence.
From the 4th century on, canons were issued by Church synods, where bishops and elders of the Church convened; later, the power to issue canons became part of the papal authority.
As early as the 4th century, canon law had grown to the point where, of necessity, canons were being collated, for ease of use. The first definite collation was created by Dionysius Exiguus, around 500. This work came to have great importance for subsequent writers in the field. A revised form was elevated to the virtue of official Church law in the Frankish church.
From around the middle of the 9th century, new canonical collations began circulating in France, containing a number of falsified canons, papal bulls, etc. - these came to be known as the "false decretals", and despite their dubious veracity, they came to influence the writing of new collations.
The creation of a satisfactory collation of canon law had to wait until aroun 1140, when the Bolognese monk Gratian systematised and collated existing canon law, in a work commonly known as the Decretals of Gratian. The Decretals are divided into three parts - one dealing with the sources of canon law, one dealing with clerical jurisdiction, and one dealing with sacraments and church offices. Though they were intended as a private manual, the Decretals rapidly gained official recognition as covering most of established Church legislation.
The legal profession in mediaeval Europe was so heavily influenced by the Decretals that the profession was now divided into two parallel fields: the legists, dealing with Roman law and the decretists, specialists in canon law. The centre of decretist studies in the middle ages was Italy, particularly the University at Bologna. Later, France became the focal point for studies in canon law.
From around 1150 until the early 13th century, papal edicts (decretales) played a great part in forming and defining canon law, which necessitated the development of new collations.
It was not until 1582, however, that these were to achieve their highest form, with the publication of the Corpus Juris Canonici (Latin: "Body of Church Law"). The Corpus Juris Canonici consists of the following four parts:
Together, the
Corpus Juris Canonici forms the basis of
Catholic canon law, even today. Though modifications to the system are still under way, the basics of the system have remained unaltered.
Along the way, the system of canon law has resisted influence from other legal systems (with the exception of Roman law, on which it was partly based). To the contrary, canon law has often influenced secular law - for instance, by promoting the gradual disappearance of pre-Christian systems of justice, such as trial by ordeal.
The influence of canon law has not gone unresisted by secular authorities - the most famous clash between secular and canon law came in the form of the investiture crises that occurred at various times, across Europe, when Church authorities fought to uphold the Church's right to appoint its own officials independent of secular authorities.
Canon law can, in many ways, be seen as the crowning achievement of the Roman Catholic Church's use of its legacy of Roman law. It has had an enormous influence in the Christian world - and remains influential even in Protestant countries, despite Martin Luther's rejection of its validity.
Useful references:
W.M. Plöchl: Geschichte des Kirchenrechts, 1953-1966
H.E. Feine: Kirchliche Rechtsgeschichte, 1964.