15 The fact is that men of the present day want to be able freely to profess their religion in private and in public. Indeed, religious freedom has already been declared to be a civil right in most constitutions, and it is solemnly recognized in international documents. The further fact is that forms of government still exist under which, even though freedom of religious worship receives constitutional recognition, the powers of government are engaged in the effort to deter citizens from the profession of religion and to make life very difficult and dangerous for religious communities. This council greets with joy the first of these two facts as among the signs of the times. With sorrow, however, it denounces the other fact, as only to be deplored. The council exhorts Catholics, and it directs a plea to all men, most carefully to consider how greatly necessary religious freedom is, especially in the present condition of the human family. All nations are coming into even closer unity. Men of different cultures and religions are being brought together in closer relationships. There is a growing consciousness of the personal responsibility that every man has. All this is evident. Consequently, in order that relationships of peace and harmony be established and maintained within the whole of mankind, it is necessary that religious freedom be everywhere provided with an effective constitutional guarantee and that respect be shown for the high duty and right of man freely to lead his religious life in society. May the God and Father of all grant that the human family, through careful observance of the principle of religious freedom in society, may be brought by the grace of Christ and the power of the Holy Spirit to the sublime and unending and "glorious freedom of the sons of God" (Rom. 8:21).
Source: Dignitatis Humanae (Vatican.va)