**ACCESSION**
Accession may be defined as an original mode of acquiring property through the incorporation or addition to one’s own property of a good that was not previously part of it and was not under one’s ownership. This right is not conferred by nature but rather established by positive laws.
Great moralists largely applied to this institution the principles of Roman law, which had become common law and had undergone long and detailed elaboration in this matter. Today, it is necessary to apply the civil law of each nation, even when dealing with ecclesiastical goods (cf., by analogy, can. 1529), save for the principles of divine and canon law.
Accession does not raise particular questions of law or morality if the things belong to the same owner or if different owners incorporate things by mutual agreement—in which case, the contract suffices. If, however, there is no agreement among the different owners, recourse must be had to the provisions of civil law, which are substantially based on the principle of equity and adopt as their criterion the maxim: *accessorium cedit principali*.
The thing to which another is subordinate is called the principal thing. If one of the things is immovable and the other movable, the latter is accessory, the former principal; if both are movable, the ranking is generally determined by the purpose, or, in the absence of other elements, by the value of the things. However, the owner of the principal thing is bound to compensate the other to the extent of the enrichment; indeed, if the accession was procured in bad faith, the owner is also bound to compensate for the damage.
Accession by fructification, which almost all moralists discuss, does not apply in Italian law, which, returning to the Roman law concept, treats this as an intrinsic expansion or evolution of property in the context of fruits (Cod. Civ. It., arts. 820-21), not classifying it among the modes of acquiring property (I. III tit. II, cap. III). In accession as it is now understood in Italian law, the extension of property does not occur through the intrinsic expansion of the thing but rather through the force of a new title arising from the occurrence of a new legal fact.
There are various ways in which accession, thus conceived, may occur. To reduce the various cases to a certain unity, one may speak of two classes of accession depending on whether the things involved are immovable among themselves or with movables, or movables among themselves, or depending on whether the act of union is primarily the work of nature or the principal factor is human industry. Following the first classification scheme, the first category of accession (between immovable things or between movables with immovables) includes the following figures: alluvion, avulsion, new island, abandoned riverbed, in which the work of nature prevails, and building, planting, in which human labor prevails over the work of nature; the second category (accession between movables) includes union, commingling, specification, etc., in which human industry still prevails.
1. **Alluvion** – Under the term *alluvion* are included the unions of earth and the increments that form successively and imperceptibly (*incrementum latens*) in lands situated along the banks of rivers or streams (Cod. Civ. It., arts. 941). **Avulsion** occurs when a river or stream forcibly detaches a considerable and recognizable part (*incrementum patens*) of a contiguous land and carries it to a lower land or to the opposite bank. In both cases, the owner of the land becomes owner of the added earth, except when the alluvion results from the regulation of the river’s course, land reclamation, or similar causes (arts. 941, 947), and, in the case of avulsion, save for the indemnity payable to the other owner within the limits of the increased value brought to the enlarged land by the avulsion (arts. 944).
A different rule applies when avulsion gives rise to a new island in the riverbed: the owner of the land from which the detachment occurred retains ownership; the same rule applies when the island is formed not by avulsion in the strict sense but by the new course of a river or stream that crosses and surrounds the land or part of the land of a neighboring owner (arts. 945). Apart from these two cases, in all others, islands and unions of earth formed in the riverbed or stream belong to the public domain (arts. 945). However, the rules regarding islands and unions of earth do not apply when the change in the riverbed results from the regulation of its course, land reclamation, or similar causes (arts. 947).
If a river or stream forms a new bed, abandoning the old one, the abandoned riverbed belongs to the owners of the lands bordering the two banks. They divide it along the midpoint of the bed, according to the frontage of each owner’s land (arts. 946). If, instead of changing its bed, the river or stream gradually shifts from one bank to the other, the land abandoned by the water belongs to the owner of the exposed bank, without the owner of the opposite bank being able to claim the lost land, *natura enim contingit* (arts. 942). If, however, human intervention is involved, such as through the regulation of river courses or land reclamation, the aforementioned rules do not apply (arts. 947).
**Building – Planting – New Works** – In general, any planting, construction, or any work done above or below the soil belongs to the owner of the soil (arts. 934) according to the classic principle: *Quidquid plantatur, seritur vel inaedificatur, totum solo cedit, radices si tamen egit*. However, it is necessary to consider the particular norms that civil law establishes for various possible cases, in relation to the ownership of the materials used in construction and similar matters, as well as the right and duty of compensation (arts. 934-38).
2. **Accessory Movables** – Between movables, accession may occur in an indefinite series of cases, which cannot all be individually contemplated by the legislator. The Italian legislator addresses three main cases: union, commingling (or mixture), and specification.
In union and commingling, the different things, though forming a single body, remain substantially distinct, as in writing, painting, weaving, metal alloys, etc. Each party retains ownership of their own thing and has the right to demand its separation if possible; otherwise, there is joint ownership in proportion to the value of the things belonging to each. However, if one of the things has a much greater value or may be regarded as principal, the owner of it acquires ownership of the whole, while remaining bound to pay the other or others the value of their thing, or, if the union occurred without their consent, the lesser of the increase in value brought to the principal thing or the value of the accessory thing, save for the right to compensation for damages in case of gross negligence (art. 939).
**Specification** is the accession of a new form to pre-existing material, so as to give rise to a new thing, a new species. If someone has used material not belonging to them to form a new thing, whether or not the material can revert to its original form, they acquire ownership of it, paying the owner the price of the material, unless the value of the material greatly exceeds that of the labor—in which case the roles are reversed (art. 940).