Pius XII says: “Can God, though it would be possible and easy for him to suppress error and moral deviation, in some cases choose to not impede these without coming into contradiction which his own infinite perfection? Can it be the case that in determinate circumstances he does not give to men any mandate to impose any duty, nor give any right to suppress, that which is erroneous and false? A glance at reality gives us an affirmative answer. It shows that error and sin are found in the world in ample measure. God reproves them, yet he allows them to exist. Thus the affirmation: religious and moral deviation ought always to be impeded, as far as possible, because their tolerance is in itself immoral and cannot be valid absolutely and unconditionally. On the other hand, God has not given to any human authority such an absolute and universal warrant either in the field of faith or in that of morals. Such a warrant is not known by either the common conviction of men, nor the Christian conscience, nor the fountain of revelation, nor the practice of the Church.” (Pius XII, Oratio, Dec. 6, 1953)
I can think of some illegal activities that should probably be decriminalized.