Definition - What does Canon Law mean?
Canon law, in its simplest form, refers to religious law that is specific to the Christian faith. Historically, it has primarily been employed by the Roman Catholic Church. As such, it is not applicable in American state or federal courts. However, it is applicable in the Vatican and in any other countries that recognize Catholicism as the "official" religion.
Justipedia explains Canon Law
Canon law is based on archaic church texts, historic papal edicts and related rulings by church-sanctioned bodies. In turn, it influenced and was influenced by English common law.
That combination of religious and secular law eventually formed the framework for familiar American laws and legal procedures. Examples of this influence include the grand jury system and some marriage laws.
Historically, canon law has also been used to adjudicate certain matters within the church. As that practice continued, it has been modified to meet church needs and functions.