NULLITY. — The law may prescribe a requirement for a legal act in various ways:
a) so that 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 lack of the requirement produces both consequences.
The act that has, or lacks, the prescribed requirements will be called, respectively, in the first case lawful or unlawful, in the second case valid or invalid, in the third case lawful and valid or unlawful and invalid.
But invalidity—which occurs when one of the requirements mentioned in b) and c) is lacking—can take different forms, depending on the importance of the missing requirement and the reason why the legislator prescribes II. For this reason, instead of speaking of the invalidity of a legal act, one more generally speaks of a defect in the act.
Setting aside terminological uncertainties in laws and doctrine (especially less recent ones), various kinds of defective acts can be distinguished, bearing in mind that it is usually positive law that determines what consequences follow from the lack of a requirement. In the first place, an act is said to be *null* when it does not produce the legal effects proper to the act one intended to perform, but either produces the effects proper to another kind of legal act (conversion of the act) or produces no effects at all (material act, which is not a legal act). This occurs above all when an act lacks a requirement so important that the legislator deems it necessary to require it even if the persons taking part in the act wish to disregard II. Typical examples of nullity are found in legal acts performed without consent or without observing the form prescribed by law, and also, in private civil law, in unlawful legal acts. With regard to the nullity of marriage, which can arise from the existence of an impediment, a defect of consent, or a defect of form, see MATRIMONIO (IV, 1).
With regard to unlawful acts, it should be noted that, while in the civil law of the State—at least within the sphere of private law—the principle holds that all unlawful legal acts, with certain exceptions, are null (cf. Cod. civ., art. 1418), in canon law the opposite principle holds, namely that a prohibited legal act is not for that reason null, unless the law attaches the sanction of nullity to the prohibition (cf. CIC, cann. 11 and 1680). The difference, however, is more apparent than real, because in the case of acts of a patrimonial nature (which are those to which the above-mentioned principle of civil law especially applies), canon law adopts the norms established by civil law (see CANONIZZAZIONE DELLE LEGGI).
It may, however, happen that a requirement, prescribed in view of certain interests, is not so indispensable for those interests that it cannot be substituted by other elements; or it may even be that those interests are equally satisfied despite the lack of a requirement. This explains why the law often establishes requirements whose lack does not produce, or does not always produce, the nullity of the act. A first instance occurs when, although the act is null, the nullity can be cured if a fact arises that is capable of substituting for the missing requirement, or a fact that shows the uselessness of that requirement: one may think, respectively, in canon law, of the convalidation or radical sanation of a marriage (cann. 1133–1141, excepting can. 1135 § 1), or of the spontaneous appearance in court to act in a cause after an invalid citation (cf. cann. 1587 § 1, 1711 § 2), or of the participation of electors in an election despite the nullity of the convocation (can. 162 § 4). In such a case one may speak of *relative nullity*, which can be cured by a subsequent fact (positive, not merely negative) that has the effect of convalidating the act (with retroactive or non-retroactive effect, as the law may determine).
Another instance may be that in which, the requirement being prescribed for the benefit of limited subjects, or the requirement not being entirely lacking but merely irregular, the law holds that if those subjects 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 lack or irregularity of the requirement, that is, if they acquiesce in it; it is not so, however, if they assert such a lack and demand that the act produce no effect. Nor need it be added that when the law follows this course it always establishes a term within which the defect of the act can be asserted, so that the uncertainty regarding its effects cannot be indefinitely prolonged. In such a case the act is *voidable*, the defect is called *voidability*, and the effects of the act are suppressed by a subject other than the interested party (generally, by a judge) through annulment (with effect generally, but not necessarily, retroactive). Since in such instances voidability is imposed by the law for the protection of the person for whose benefit the missing or irregular requirement was prescribed, that person can no longer seek annulment of the act if, even before the term for bringing the action has expired, they have ratified the act after the defect has ceased.
Examples of voidability are generally found in cases in which the author or authors of the act were legally incapacitated, and in cases in which they performed the act voluntarily but the will was formed irregularly because of the interference of a disturbing cause (defect of will: error, violence, or fraud), while it is probable that, had such a cause not intervened, the will either would not have existed or would have been different. Many of the cases in which the CIC speaks of rescission or of a rescindible act (cf. can. 103 § 2, 104, 506 § 4, 1684–87), of irritatio at the instance of the interested party (cf. can. 162 § 2), of the possibility of restitutio in integrum (cann. 1687–89), etc., fall under the concept of voidability.
In civil law, the terms *rescindibility* and *rescission* of an act are used when it is admitted that one of the parties may ask that the act be annulled because the proper proportion between the various parties has not been observed, as, for example, if in a contract there is what is called *lesione enorme*, that is, a considerable disproportion between the performance of one party and that of the other (cf. Cod. civ. art. 763 and 1447–52; CIC can. 1684 § 2). Rescindibility may be considered a subspecies of voidability, although doctrine has remained hesitant to admit this and civil laws regulate the two in notably different ways.
It may finally happen that, although in a juridical act no requirement is lacking or irregular, yet it may, for pre-existing reasons or, more frequently, for reasons arising subsequently, be little consonant with ethical norms or otherwise unsuitable, so that the legislator deems it expedient to grant to the author of the act or to others the power to remove or alter its effects (if the right belongs to the author of the act, it is spoken of as ius poenitendi): this phenomenon may be collectively indicated by the term revocation, although this word is more commonly used only for the case in which it is exercised by the author himself of the act. Under this heading fall, besides the well-known examples of bilateral revocation of contracts, and unilateral revocation of testaments and donations (cf. also CIC can. 583 n. 2, and 1536 § 4), irritatio (can. 1312 § 1 and 1320), suspensio (can. 1312 § 2), dispensatio (can. 1313 and 1320), commutatio (can. 1314 and 1320) and relaxatio (can. 1317 § 2) of a vow or an oath. The difference between revocation and annulment lies in this: in the latter, once the lack of a requirement has been ascertained, he who has the power to annul must pronounce the annulment; in the former, on the other hand, it is left to the discretion of him who has the power to judge whether it is expedient or not to nullify the effects of the act.