31 When we pay honor to the princely dignity of Christ, men will doubtless be reminded that the Church, founded by Christ as a perfect society, has a natural and inalienable right to perfect freedom and immunity from the power of the state; and that in fulfilling the task committed to her by God of teaching, ruling, and guiding to eternal bliss those who belong to the kingdom of Christ, she cannot be subject to any external power. The State is bound to extend similar freedom to the orders and communities of religious of either sex, who give most valuable help to the Bishops of the Church by laboring for the extension and the establishment of the kingdom of Christ. By their sacred vows they fight against the threefold concupiscence of the world; by making profession of a more perfect life they render the holiness which her divine Founder willed should be a mark and characteristic of his Church more striking and more conspicuous in the eyes of all.
Source: Quas Primas (Vatican.va)