The Roman Catholic Church, even when recognized as the state religion, is nowhere "established" in the sense of being identified with the state, but is rather an imperium in imperio which negotiates on equal terms with the state, the results being embodied in concordats (q.v.) between the state and the pope as head of the Church.
The concordats are of the nature of truces in the perennial conflict between the spiritual and secular powers, and imply in principle no surrender of the claims of the one to those of the other.
As a matter of fact, however, the revolution caused by the secularization of the ecclesiastical states in 1803 practically put an end to the system, and the servitia have either been commuted via gratiae to a moderate fixed sum under particular concordats, or are the subject of separate negotiation with each bishop on his appointment.
Having made this remark, we must distinguish between the countries which are still subject to the system of concordats and other countries.
It is plain that the agreements under the concordats have a certain action upon a number of points in the canonical laws; and all these points go to constitute the local concordatory law.