Canon Law is the oldest continuous legal system in the western world. It is an internal system of law within the Catholic Church which respects civil law, as long as civil law is not in conflict with what the Church sees as just and moral. The current Code of Canon Law was promulgated in 1983 by Pope John Paul II. The 1983 Code is a revision of the previous 1917 Code. The revision was a direct result of the Second Vatican Council (1962-65), and the goal of the revision process was to translate the Second Vatican Council’s teaching into the 1983 Code.
There are 1752 canons (laws) in the 1983 Code of Canon Law, and those canons cover much of the law of the Church, but there are other laws, norms, precepts, and rules listed in other places. The second law or canon of the 1983 Code states that “for the most part” the code does not define liturgical rites or how they are to be celebrated. Those norms are found in the beginning of official liturgical rite books. There are also precepts issued within a diocese that are followed within that diocese, which may differ from precepts in another diocese nearby (e.g. age for Confirmation). Religious orders/congregations each have a general rule, which encompasses many rules for the internal governing of the order and the protection of its members. Those rules do not apply to members of a diocese, who are not members or seeking to be members of the religious order/congregation.
The first canon (law) in the 1983 Code can seem a bit confusing and affects fewer members of the Diocese of San Jose than the second canon (above), which affects us all. Still the first canon is very important. It ways, “The canons of this Code  regard only the Latin Church.” The Latin Church is the one the vast majority of U.S. Catholics might believe is synonymous with the Catholic Church, but the Universal Catholic Church is bigger than the Latin Church. There are Eastern Rite expressions of the Universal Catholic Church that are loyal to papal authority but are considered churches themselves. Within the geographical boundaries of the Diocese of San Jose, there are five Eastern Catholic Churches, who each have their own bishops outside the territory of the Diocese of San Jose, even though the Bishop of San Jose still has a supervisory authority over those Churches: Byzantine (Ruthenian) Catholic Church, Melkite-Greek Catholic Church, Syro Malabar Catholic Church, Chaldean Catholic Church, and Ukrainian-Greek Catholic Church. There are others too, but not in our diocese. In 1990 Pope John Paul II promulgated the Eastern Code of Canon Law, which has the canons for those Eastern Churches. So there are two codes of Canon Law with many similarities, but the Eastern Code was needed to honor the distinct traditions of those Eastern Churches, which are Catholic but not “Latin”. Hopefully, that explains the first canon (law) in the 1983 Code of Canon Law.
Both codes of canon law cover many areas of church ministry, and many of the laws are very pastoral. There are sections on sacraments, parishes, dioceses, Catholic education, religious orders, ownership of goods, protection of rights, and ecclesiastical penalties—to mention a few. Both codes of Canon Law are accessible on the internet. To understand many of the canons a commentary is necessary (e.g. New Commentary on the Code of Canon Law, edited by Beal, Coriden, and Green, 2000). Or, you can call the canonists working in the Tribunal of our diocese.
Finally, the last canon of the Code of 1983 is sometimes referred to as the Supreme Law of the Church. The last part of that final canon says: “…the salvation of souls, which must always be the supreme law in the Church, is to be kept before one’s eyes.”