The religious acts whereby men, in private and in public and out of a sense of personal conviction, direct their lives to God transcend by their very nature the order of terrestrial and temporal affairs. Government, therefore, ought indeed to take account of the religious life of the people and show it favor, since the function of government is to make provision for the common welfare. However, it would clearly transgress the limits set to its power were it to presume to direct or inhibit acts that are religious.Declaration on Religious Liberty
(Dignitatis Humanae), no. 3December 7, 1965
Much more to read here.