67 Those who hold the reins of government should not forget that it is the duty of public authority by appropriate laws and sanctions to defend the lives of the innocent, and this all the more so since those whose lives are endangered and assailed cannot defend themselves. Among whom we must mention in the first place infants hidden in the mother's womb. And if the public magistrates not only do not defend them, but by their laws and ordinances betray them to death at the hands of doctors or of others, let them remember that God is the Judge and Avenger of innocent blood which cried from earth to Heaven.
Source: Casti Connubii (Vatican.va)