The Roman Catholic Church has the oldest continuously functioning legal system in the Western World. It is older than the common and European civil law traditions. What began with rules ("canons") adopted by the Apostles themselves at the Council of Jerusalem in the First Century led to a highly complex and original legal system that included norms of the New Testament, of the Hebrew (Old Testament), Roman, Visigothic, Saxon, and Celtic legal traditions with thousands of years of human experience.
Baker, J.H. (2002) An Introduction to English Legal History, 4th ed. London : Butterworths, ISBN0-406-93053-8
The Episcopal Church (2006) Constitution and Canons, together with the Rules of Order for the Government of the Protestant Episcopal Church in the United States of America, otherwise known as The Episcopal Church, New York : Church Publishing, Inc.
Robinson, O.F.,Fergus, T.D. and Gordon, W.M. (2000) European Legal History, 3rd ed., London : Butterworths, ISBN0-406-91360-9