A canonical territory is, in some Christian denominations, a geographical area seen as belonging to a particular bishop or Church as its own when it comes to ecclesiastical matters, whether by tradition or by canon law. The concept is found both in the Eastern Orthodox Church and Catholic Church. According to Andriy Mykhaleyko, the expression "canonical territory" is "rather difficult to define as it can refer to a variety of different aspects, from an ecclesiological, geographical, and cultural entity to the territorial or canonical jurisdiction of a church as an expression of its local community, or the pastoral theological care of the faithful in a particular territory." Bishop Hilarion Alfeyev, of the Russian Orthodox Church, asserts that: [t]he model of church organization that was formed during the first three centuries of Christianity was based on the principle of "one city-one bishop-one Church", which foresaw the assignment of a certain ecclesiastical territory to one concrete bishop." In accordance with this principle, the "Canons of the Apostles" and other canonical decrees of the ancient Church point to the inadmissibility of violating the boundaries of ecclesiastical territories by bishops or clergy. Some canons of the Canons of the Apostles state that: the bishop should not leave his diocese and go over to another without authorization (can. 14); the bishop may not ordain outside the boundaries of his diocese (can. 35); when transferring to another city, excommunicated clergymen or laymen cannot be accepted into communion by another bishop (can. 12); clergymen who go over to another diocese without the consent of their bishop are deprived of the right to serve (can. 15); prohibition of serving or excommunication of a clergyman imposed by one bishop cannot by removed by another bishop (can. 16, 32). "In defining the boundaries of ecclesiastical territories, the Fathers of the ancient undivided Church took into account civil territorial divisions established by secular authorities," according to Alfeyev.