Chapter VII. On Unwritten Law, or on Custom

Custom considered causally, or as others say, custom of fact, is the frequency of similar acts of some community; but regarded formally, or custom of right, it is a certain right arisen from the frequency of similar acts of some community. Custom of fact often is nothing but an abuse, and the discourse here is not about it, but only about custom of right.

Custom is chiefly divided into custom beside the law, according to the law, and against the law. The first is a certain new law, which therefore constitutes right where written law commands or prohibits nothing. The second is that which interprets or confirms a law already existing, and this constitutes right, not where law is wholly lacking, but where it is lacking as regards interpretation, or firmness and observance. Finally the third is that which is established against the reception of a law, or for abolishing a law already received, and this establishes derogatory right where a written abrogating law is lacking. - Cf. Bouix, de Princip., pp. 350 and seq.

I say. Custom, clothed with the due conditions, introduces right, and has force after the manner of written law. This is clear from very many places of canon law, especially from cap. In his, Dist. 11, from the unanimous consent of the Doctors, and specially from St. Thomas, 1-2, q. 97, art. 3.

Question 1. What are the conditions required for legitimate custom?

Response. Several are enumerated by the Canonists; the chief ones are the following:

(a) On the part of the custom itself it is required that it be reasonable, not indeed in this sense, that it is not sinful, for ordinarily those who first introduce it against the law sin, but that it is not against divine or natural right, nor breaks the nerve of ecclesiastical discipline. - Cf. St. Thom. ib. - Bouix, de Princip., p. 362.

(b) A community which is at least capable of receiving ecclesiastical law can introduce a custom which obtains the force of law (Can. 26), and the reason is that custom is a law which binds the whole community, and therefore must arise from the whole community. Cf. Scavini, n. 285. - Bouix, de Princip., p. 357.

(c) On the part of the acts it is required that these be 1st. free, because otherwise the efficient cause would be lacking, namely the consent of the people; 2nd. frequent and uniform, otherwise it could not be known that this consent is present; 3rd. continuous, because prescription ceases through interruption; 4th. done with the intention of obliging themselves or of introducing a custom, because custom is a law which does not oblige unless there is present a will of binding; 5th. of long duration, otherwise prescription would not be had. - Cf. Bouix, ibid.

(d) Custom in the Church obtains the force of law solely from the consent of the competent ecclesiastical Superior (Can. 25). For if the Superior in no way consents, and a fortiori if he resists, nothing can be established by subjects for the good of the community. Personal consent is either express or tacit; the first is easily understood; the other is present when the Prince knows the custom and yet does not contradict it, though he can conveniently contradict it. But legal consent, which is also called general or juridical, is that which is given through law, or through right itself, which in advance and universally approves all reasonable and legitimately prescribed customs. For consent of this kind it is not required that the Prince know the custom. The opinion of the Doctors is most common that legal consent is admitted by canon law as sufficient for strengthening a custom, provided that it is reasonable and has endured for the time required for prescribing. This is clear from cap. Cum tanto, 11, tit. 4, de Consuetudine, lib. 1, Decret. - Cf. Reiffenstuel, in 1, Decret., tit. 4, § 5, n. 138. - Bouix, de Princ., p. 370.

Question 2. Whether length of time is always required, and what sort it ought to be?

Response. If the Prince expressly or tacitly consents to the custom, length of time is not required; for as soon as the will of the Prince accedes to the will of the subjects, all are obliged. But it is required if custom is to be strengthened through legal consent: for thus the laws demand, and indeed wisely, lest more quickly than is fitting, while the Prince is unaware, new laws be introduced or old ones be abrogated.

§ 1. No custom can in any way derogate from divine right, whether natural or positive; but neither does it bring prejudice to ecclesiastical right, unless it has been reasonable and legitimately prescribed through forty continuous and complete years; but against an ecclesiastical law which contains a clause prohibiting future customs, only a reasonable centenary or immemorial custom can prescribe.

§ 2. A custom which is expressly reprobated in law is not reasonable (Can. 27).

A custom beside the law, which has knowingly been observed by the community with the intention of obliging itself, introduces law, if likewise it has been reasonable and legitimately prescribed through forty continuous and complete years (Can. 28). - Cf. St. Alphonsus, n. 107; and Hom. Ap., n. 11.

Note. - With the prescript of can. 5 remaining firm, a custom against the law or beside the law is revoked by a contrary custom or law; but, unless it shall have made express mention of the same, a law does not revoke centenary or immemorial customs, nor does a general law revoke particular customs (Can. 30).