Vigilanti Cura §51

⁵¹ Were it possible, it would in itself be desirable to establish a single list for the entire world because all live under the same moral law. Since, however, there is here question of pictures which interest all classes of society, the great and the humble, the learned and the unlettered, the judgment passed upon a film cannot be the same in each case and in all respects. Indeed circumstances, usages, and forms vary from country to country so that it does not seem practical to have a single list for all the world. If, however, films were classified in each country in the manner indicated above, the resultant list would offer in principle the guidance needed.