Third Question: On the Mutability of Human Law

298. Human law is mutable. - Human law, although negatively it is perpetual because of itself it is stable and always endures like the community, nevertheless positively is not perpetual, because what it commands from its nature is not necessary: "in mutable things," says St. Thomas, "there cannot be anything remaining altogether immutably" (a. 1, ad 2).

Whence human law can be changed either a) on the part of the legislator, who gradually wishes to lead subjects to a greater good; or b) on the part of the matter, which on account of diverse circumstances of times and places becomes less useful to the end; or c) on the part of the subjects, for whom diverse laws are expedient according to their diverse conditions (cf. for ecclesiastical law, Lateran Council IV, c. 26; and Trent, sess. 14, c. 1 and 2; sess. 21, c. 2).

Nevertheless they are not easily to be changed (especially organic laws of political and administrative right), even when some improvement is possible. It is proved:

Human law is rightly changed insofar as, by its change, provision is made for common utility. But the very change of law of itself is harmful and brings detriment to the common good: "for the observance of laws," says St. Thomas (a. 2), "custom has very great force, to such an extent that those things which are done against common custom, even if they are lighter of themselves, seem graver; whence when law is changed, the constraining force of law is diminished, insofar as custom is removed." Therefore human law should never be changed unless so much is recompensed to common utility as is derogated from it by the change. This happens in two cases:

a) either from the fact that some very great and very evident utility comes from the new law;

b) or from the fact that there is very great necessity from this, that the accustomed law either contains manifest iniquity or its observance is very harmful.

299. Human law can be changed in two ways:

So that the law itself ceases and we are excused from it generally: either intrinsically by the total cessation of the end itself (when the reason of the law ceases, its disposition ceases, and when the end ceases, the precept ceases), or extrinsically, both by revocation, that is, abrogation and derogation, and also by contrary custom (with the consent of the legislator). Nevertheless, in present-day law neither custom nor cessation of the end is admitted unless it is expressly indicated by the law, nor is it necessary in present-day society: for in these cases the abrogation itself of the law can be proposed by members of the legislative assembly.

So that in some way only the obligation of the law ceases (or at least is not applied) in a determined case, and we are excused from transgression of the law, whether formal and subjective only, which happens by ignorance, or also material and objective, which happens intrinsically by inability (which is judged by epikeia), and extrinsically by dispensation, to which privilege pertains.

Nevertheless in present-day law a) dispensation cannot validly be conceded except in rare cases determined by it, b) ordinarily ignorance of the law is not admitted in the external forum, because all are judged to use diligence for knowing the laws; hence although one who is ignorant is innocent before God, before a judge he can be held as guilty: then juridical fault is present, and if the law establishes a penalty, after the sentence of the judge there is an obligation to sustain it by reason of preserving external order and the common good, otherwise all would say that they were ignorant of the laws.

All these things will be more apparent from their application to ecclesiastical law. This will be discussed below.