Summa summae S. Thomae, Tomus II

[Custom is twofold¹ : one of fact, the other of right. Custom of fact is defined by St. Thomas : « Frequent acting freely in the same manner. » Custom of right, which follows from custom of fact, is defined by Isidore, book V Etymol., c. 3, cited chapter 5, dist. 1 : « A certain right instituted by manners [that is, by frequent acts], which is taken for law when law fails. » Here chiefly custom of fact is treated.]

St. Thomas attributes three things to custom² : first, that it introduce law, namely when it exists apart from law and presupposes none; secondly, that it abrogate a law laid down and received; thirdly, that it interpret it. But custom can obtain these three in a twofold way : 1° by way of connivance, when the superior personally consents tacitly or expressly to the custom, to which no determined time is required; 2° by way of prescription, when the custom has prevailed for a certain time, with consent concurring, if not personal, at least juridical or legal, of the superior, as will be explained below.

Whether therefore and how custom can obtain these three things, we inquire. Wherefore

I say 1° : Reasonable custom can introduce law where there is none, as well by way of connivance as by prescription³.

[It is proved from both laws. From canonical law, cap. In his, dist. 11, where it is said from Aug. ad Casulanum, epist. 36 : « In those matters concerning which divine Scripture has established nothing certain, the custom of the people of God or the institutes of our forefathers are to be held for law. And as corrupters of divine laws, so despisers of ecclesiastical customs are to be coerced. » Likewise cap. Illa, dist. 12, from the same Aug. ad Januarium, epist. 54 ; who in each epistle reports the celebrated saying of Ambrose : « Whichever church you come to, keep its custom. » And elsewhere. From civil law. L. De quibus, ff de legibus, and elsewhere.]

It is proved by reason. In reasonable custom can concur all the things required for law, namely honest matter useful to the common good, the intention of binding oneself and legitimate authority, whether of the community, if it be free, or of the prince manifestly approving, either personally or legally, that custom and intention. Therefore.

I said : « Of the prince approving, either personally or legally, » because a twofold consent of the prince is distinguished, one personal, the other juridical or legal : Personal, when the superior, aware of the custom, approves it, either expressly by word or by some manifest act, or tacitly, by not resisting it while he easily could. Juridical or legal consists in this, that the laws or predecessors of the present superior have declared and enacted that such custom introduces law; to which consent, as is plain, it is not required that the custom become known to the superior. That therefore custom may introduce law by way of connivance, personal consent is required, at least tacit; but that it may introduce it by way of prescription, legal consent suffices.

[You will ask whether all customs long-lasting and general obtain the force of law.

Answer. Customs which consist in the frequent repetition of the same acts, however long-lasting and general they be, do not obtain the force of law unless they were observed with the mind of binding oneself. The reason is, because custom is taken for law. But law is constituted through the will of obliging. Therefore. Whence the custom of saluting B. M. V. thrice a day at the tolling of the bell, of purifying oneself with blessed water at the entrance of the church, etc., never obtained obligatory force of law, because these acts were always frequented from mere devotion. It is known moreover whether a custom was introduced with the mind of binding oneself, if it be observed constantly and universally and not without considerable inconvenience; if transgressors are punished; if pious men commonly so judge. But in doubt whether a custom be from devotion or obligation, whether under grave or under light matter, whether it oblige under sin or only under penalty, the more benign part is to be held; for no law obliges unless it stand established concerning it. So St. Ligor., lib. I, n. 107.]

I say 2° : Reasonable custom can abrogate human law, even irritant, or derogate from it, as well by way of connivance as by prescription⁴.

Of the way of connivance there is no difficulty, because law hangs upon the will of the legislator; whence, the will of the legislator being changed, and this manifested outwardly, the law ceases. But through free connivance toward a custom contrary to the law is manifested in fact the change of will in the legislator. Therefore. I said : « Free connivance, » so that the legislator can easily hinder it and does not hinder it; for if he tolerate it because he cannot resist, or defer to another time, it is not free consent sufficient to abrogate law by way of connivance.

The second part is proved from both laws. From canonical law. Cap. Cum tanto de consuetudine, Decretal. lib. I, tit. 4, c. 11, it is said : « Although long-standing custom has no mean authority, yet it shall not prevail so far as to generate prejudice against positive law itself, unless it be reasonable and legitimately prescribed. » By which exception the canon plainly signifies that reasonable custom legitimately prescribed can derogate from human law. From civil law, L. De quibus, ff de legibus : « Most rightly has this been received, that laws are abrogated not only by the suffrage of the legislator, but also by the tacit consent of all, through disuse. »

It is proved by reason. Human laws are subject to the authority and will of men, no otherwise than other human things and rights. But human things and rights can be changed and transferred independently of the will of their lords through the authority of law, as happens in prescription. Therefore likewise human laws can be changed through the authority of law, independently of the personal will of legislators. — I subjoin. But the laws decree that reasonable custom legitimately prescribed prevail over human law, as is plain from the laws praised above. Therefore.

Hence you will infer that no determined time is required in order that custom abrogate law by way of connivance, but that it suffice that connivance or personal consent of the legislator stands established; because the law ceases not by right but by the changed will of the legislator himself. When however one proceeds by way of prescription, determined time is required; because then it ceases not from the changed will of the legislator, but from the disposition of law, and therefore time determined by law is required in order to prescribe legitimately. Whence the common opinion is, that in order that custom prescribe against civil law, ten years are required; against ecclesiastical law, forty years; because thus common law disposed for the prescription of other civil and ecclesiastical rights.

[Prescription of forty years seems required against ecclesiastical laws, from cap. De quarta, lib. II Decretal., tit. 26 de praescript. and cap. Ad aures, ibid., where is read : « Prescriptions of forty years exclude every action altogether. » But Lessius, lib. II, chapter 6, dub. 14, n. 17, and others cited among the Salmanticenses, de Legib., chapter 6, punct. 3, § 2, n. 17, say probatively that ten years suffice, whether the laws be received or not; because no greater reason is to be had of custom against ecclesiastical law than against civil, since no law distinguishes between these laws. Lessius answers moreover to the texts cited, that they speak not of laws, but of rights and goods immovable of the Church to be prescribed; but under the name of rights the laws of the Church do not come. So St. Ligor., lib. I, n. 139.

You will ask 1° whether good faith be required in order to prescribe against law.

Answer negatively, with St. Ligorio, lib. I, n. 107. Even by sinning can custom be made. Salmant., de Legib., chapter 6, punct. 3, § 1, n. 11, with Suarez. For custom holds a threefold state. In the beginning, all sin who introduce custom against law. In progress, those sin not who now use it, already introduced by their forebears, but they can be punished by the prince. At the end they sin not, nor can they be punished, who use it now prescribed. So Salmant., ibid. n. 13, and others. The reason is, because, when custom is clothed with all the conditions required, among them is found the consent of the legislator such as was described above.

You will ask 2° whether custom can prevail, if a law be passed with the clause : « Notwithstanding any custom whatsoever. »

Answer. The clause is commonly understood of a contrary custom already existing, not indeed of a future one. Salmant., de Legib., chapter 6, punct. 4, § 2, n. 43, and others. But if the clause reject any custom whatsoever, even future, Salmant., ibid., n. 43, with Suarez, say it is more probable that such a custom can abrogate the law. For if some custom must be judged unreasonable at the time the law is passed, it can become reasonable at future time, unless it be adverse to natural or divine law. St. Ligor., ibid., n. 108.]

I say 3° : Custom can interpret law⁵.

It is plain from law, cap. Cum dilectus, Decretal. lib. I, tit. 4, de consuetudine, etc. L. Si de interpretatione, ff de legibus. In both custom is called « the best interpreter of laws. »

[Interpretation moreover is twofold : one doctrinal, according to the mind and sense of the legislator; the other authentic, which proceeds from a superior and has the force of introducing some sense which is received for new law, although perchance it agree not with the first intention of the legislator. In both ways custom can interpret human law; but in the former way only natural and divine law.]