A more thorough explanation:

Jus canonicum is a Latin term that refers to the body of western ecclesiastical law known as canon law. This law was compiled from the 12th to 14th centuries and has grown steadily since then. It is now codified in the Codex Juris Canonici of 1983, which replaced the previous version from 1918.

Canon law is a body of law developed within a particular religious tradition, and it regulates the affairs of the Church. It has had a significant influence on the development of English law, as many judges in the royal courts during the early Middle Ages were ecclesiastics familiar with the chief doctrines of canon law.

For example, canon law has influenced the law of marriage and divorce in many countries. In the United States, for instance, canon law has been used to determine the validity of marriages in cases where one or both parties are Catholic.

Another example of the influence of canon law is in the regulation of religious societies. Canon law provides guidelines for the establishment and governance of religious orders, such as monasteries and convents.

In summary, jus canonicum refers to the body of western ecclesiastical law known as canon law, which regulates the affairs of the Church and has had a significant influence on the development of English law and the regulation of religious societies.