Aquinas, too, holds that unjust laws (that is, laws that do not accord with or derive from the law of nature) do not have the force of law; they are, rather, corruptiones legis–corruptions of the law. In response to objections concerning the seemingly adiaphorous nature of some human legislation, the diversity of laws among peoples, and the difficulty of giving a rational account of at least some of those laws, Thomas writes:
Respondeo dicendum quod, sicut Augustinus dicit, in I de Lib. Arb., non videtur esse lex, quae iusta non fuerit. Unde inquantum habet de iustitia, intantum habet de virtute legis. In rebus autem humanis dicitur esse aliquid iustum ex eo quod est rectum secundum regulam rationis. Rationis autem prima regula est lex naturae, ut ex supradictis patet. Unde omnis lex humanitus posita intantum habet de ratione legis, inquantum a lege naturae derivatur. Si vero in aliquo, a lege naturali discordet, iam non erit lex sed legis corruptio. (ST I-II, Q. 95, Art. 2)
I answer that it must be said that, as Augustine says in Book 1 of On the Freedom of the Will, “That [law] which is not just does not seem to be a law.” Whence [it follows that], in so far as it partakes of justice, it partakes of the virtue1 of law. Moreover, in human affairs something is called just because it is correct according to the rule of reason. The first rule of reason, however, is the law of nature, as is evident from what was said above. Whence every law established by man partakes of the reason that belongs to law2 in so far as it is derived from the law of nature. But if in anything it is inconsistent with natural law, it will no longer be law, but a corruption of law.3
- Or “power.”
- That is, to law as it actually is, objectively, in the rational order created by God.
- The translation is my own. Another is here.