Libertas §10

¹⁰ From this it is manifest that the eternal law of God is the sole standard and rule of human liberty, not only in each individual man, but also in the community and civil society which men constitute when united. Therefore, the true liberty of human society does not consist in every man doing what he pleases, for this would simply end in turmoil and confusion, and bring on the overthrow of the State; but rather in this, that through the injunctions of the civil law all may more easily conform to the prescriptions of the eternal law. Likewise, the liberty of those who are in authority does not consist in the power to lay unreasonable and capricious commands upon their subjects, which would equally be criminal and would lead to the ruin of the commonwealth; but the binding force of human laws is in this, that they are to be regarded as applications of the eternal law, and incapable of sanctioning anything which is not contained in the eternal law, as in the principle of all law. Thus, St. Augustine most wisely says: "I think that you can see, at the same time, that there is nothing just and lawful in that temporal law, unless what men have gathered from this eternal law."(5) If, then, by anyone in authority, something be sanctioned out of conformity with the principles of right reason, and consequently hurtful to the commonwealth, such an enactment can have no binding force of law, as being no rule of justice, but certain to lead men away from that good which is the very end of civil society.