NULLITY. — The law may prescribe a requirement for a juridical act in various ways: a) so that performing the act is unlawful if the requirement is lacking; b) so that, in such a case, some or all of the legal effects proper to that act do not arise; c) so that the absence of the requirement produces both consequences. An act that does or does not possess the prescribed requirements is accordingly said, in the first case, to be lawful or unlawful; in the second case, valid or invalid; in the third case, lawful and valid or unlawful and invalid.
But invalidity, which therefore exists when one of the requirements referred to in letters b and c is lacking, may assume different forms, depending on the importance of the missing requirement and the reason why the legislator prescribes II. Hence, more generally, one speaks of a defect rather than of the invalidity of a juridical act.
Leaving aside the terminological uncertainties of legislation and doctrine (especially earlier doctrine), various kinds of defective acts may be distinguished, bearing in mind that, as a rule, it is positive law that establishes the consequences of the absence of a requirement. First, an act is called null when it does not produce the legal effects proper to the act that was intended to be performed, but either produces the effects proper to another kind of juridical act (conversion of the act), or produces none at all (a material act, which is not a juridical act). This occurs especially when an act lacks a requirement of such importance that the legislator considers it necessary to demand it even if the persons taking part in the act wish to dispense with II. Typical examples of nullity are found in juridical acts performed without intent or without observing the form prescribed by law, and also, in private civil law, in unlawful juridical acts. In particular, with regard to the nullity of marriage, which may result from the existence of a diriment impediment or a defect of consent or of form, V. MATRIMONIO (IV, 1).
With regard to unlawful acts, it should be observed that, whereas under the law of the State, at least within the sphere of private law, the principle applies that all unlawful juridical acts, subject to certain exceptions, are null (cf. Civil Code, art. 1418), in canon law the opposite principle applies: a juridical act that is prohibited is not for that reason alone null, unless the law accompanies the prohibition with the sanction of nullity (cf. CIC, cann. 11 and 1680). The difference, however, is more apparent than real, because, when acts with a patrimonial content are concerned (the acts to which the stated principle of civil law applies above all), canon law adopts the rules established by civil law (v. CANONIZZAZIONE DELLE LEGGI).
It may, however, happen that a requirement prescribed with a view to certain interests is not so indispensable to those interests that it cannot be replaced by other elements; or it may even be that the interests themselves are equally satisfied despite the absence of a requirement. This explains why the law often establishes requirements whose absence does not produce, or does not always produce, the nullity of the act. One initial possibility occurs when, although the act is null, the nullity can be remedied if a fact capable of replacing the missing requirement subsequently occurs, or a fact occurs that demonstrates the uselessness of that requirement: in canon law, one may think, respectively, of the convalidation or radical sanation of Marriage (cann. 1133–1141, with the exception of can. 1135 § 1), and of voluntary appearance in court ad causam agendam after an invalid citation (cf. cann. 1587 § 1, 1711 § 2), or of the intervention of the electors in an election despite the nullity of the convocation (can. 162 § 4). In this case one may speak of relative nullity, remediable by a subsequent fact (positive, not merely negative) whose effect is to validate the act, with retroactive effect or without it, according to what the law provides.
Another possibility, however, may be that, since the persons in whose interest the requirement is prescribed are limited in number, or since the requirement is not wholly absent but merely irregular, the law considers that, if those persons do not wish to prevent the act from producing its effects, there is no interest in denying those effects. The act is therefore valid, and remains so if the interested parties tolerate the absence or irregularity of the requirement, that is, acquiesce in it; this is not the case, however, if they assert that absence and demand that the act produce no effect. It goes without saying that, when the law follows this course, it always establishes a period within which the defect in the act may be invoked, so that uncertainty concerning its effects can never be prolonged indefinitely. In this case the act is voidable, the defect is called voidability, and the effects of the act are suppressed by a person other than the interested party (generally, by the court), through annulment, generally, though not necessarily, with retroactive effect. Since, in such cases, voidability is imposed by law in the interest of the person for whose protection the missing or irregular requirement is prescribed, that person can no longer request annulment of the act when, although the period for bringing the relevant action has not yet expired, he or she has ratified the act after the defect has ceased to exist. Examples of voidability are generally found in cases in which the author or authors of the act were legally incapable, and in cases in which they performed the act voluntarily but their will was formed irregularly through the interference of a disturbing cause (defect of will: mistake, violence, or fraud), whereas it is likely that, had that cause not intervened, the will would either not have existed or would have been different. Many of the cases in which the CIC speaks of rescission or of a rescindable act (cf. cann. 103 § 3, 104, 506 § 4, 1684–87), of irritatio at the request of the interested party (cf. can. 162 § 2), of the possibility of restitutio in integrum (cann. 1687–89), and so forth, fall within the concept of voidability.
In civil laws, an act is said to be rescindable, and rescission is spoken of, when one of the parties is permitted to request that the act be set aside because the proper proportion between the various parties has not been observed, as, for example, when a contract involves so-called enormous lesion, that is, a considerable disproportion between one party’s performance and the other’s (cf. Civil Code, arts. 763 and 1447–52; CIC can. 1684 § 2). Rescindability may be regarded as a subcategory of voidability, although legal doctrine is reluctant to admit this and civil laws regulate the two matters in notably different ways.
Finally, it may happen that, although no requirement is lacking or irregular in a juridical act, the act may nevertheless, for pre-existing reasons or, more frequently, for reasons arising subsequently, be insufficiently consonant with ethical norms or otherwise inappropriate; the legislator may therefore deem it expedient to grant the author of the act or another person the power to remove or alter its effects (if the right belongs to the author of the act, this is referred to as ius poenitendi): this phenomenon may be designated collectively by the name of revocation, although that term is more commonly used only in cases where it proceeds from the author himself. It includes, in addition to the familiar examples of the bilateral revocation of contracts and the unilateral revocation of wills and donations (on which cf. also CIC cann. 583 n. 2, and 1536 § 4), the irritatio (cann. 1312 § 1 and 1320), the suspensio (cann. 1312 § 2), the dispensatio (cann. 1313 and 1320), the commutatio (cann. 1314 and 1320), and the relaxatio (can. 1317 § 2) of a vow or oath. The difference between revocation and annulment consists in the fact that, in the latter case, once the absence of the requirement has been established, whoever has the power to annul must pronounce the annulment; in the former, however, it is left to the discretion of whoever possesses the power to judge whether or not the effects of the act should be nullified.