A written constitution is an instrument which enumerates and defines the rights and duties of government, distributes its powers, prescribes the manner of their exercise, and limits them to the end that the liberties of the citizens may be preserved. Since the purpose of government is to protect human rights, not to destroy them, it follows that the charter by which a government operates cannot contain a grant of unlimited power. For the exercise of such power would be tyranny, inasmuch as it would tend to destroy rights which both the natural and the positive laws of God place beyond the jurisdiction of men. Hence, in the commonly accepted American doctrine, a constitution vests the government with such rights and powers as are necessary for the proper exercise of its just functions, and at the same time forbids it to encroach upon rights of a higher order which come to men, not from the people, nor from the State, nor from any aggregation of States, but from the Creator of both men and States, almighty God. This conception is wholly in keeping with the teaching of the Catholic Church.
Then they cited the 1888 encyclical of Pope Leo XIII, Libertas praestantissimus:
(Liberty of conscience) may also be taken to mean that every man in the State may follow the will of God, and, from a consciousness of duty and free from every obstacle, obey His commands. This, indeed, is true liberty, a liberty worthy of the sons of God, which nobly maintains the dignity of man, and is stronger than all violence or wrong—a liberty which the Church has always desired and held most dear. This is the kind of liberty the apostles claimed for themselves with intrepid constancy, which the apologists of Christianity confirmed by their writings, and which the martyrs in vast numbers consecrated by their blood.