- The content on this page originated on Wikipedia and is yet to be significantly improved. Contributors are invited to replace and add material to make this an original article.
Accessio was a legal term in Ancient Roman Law which signified that when two things are united in such ways that one is considered a component part of the other, one is considered the principal, and the other is considered to be an accession or addition to it.
Sometimes it may be doubtful which is to be considered the principal thing, and which the accession. But the owner of the principal, whichever it is, also became the owner of the accession. The most undisputed kind of accessio is that which arises from the union of a thing with the ground; and when the union between the ground and the thing is complete, the thing belongs to the owner of the ground. Thus if a man builds on the ground of another man, the building belongs to the owner of the ground, unless it is a building of a moveable nature, like a tent; for the rule of law is superficies solo cedit. A tree belonging to one man, if planted in the ground of another man, belongs to the owner of the ground as soon as it has taken root. The same rule applies to seeds and plants.
If one man wrote on a papyrus (chartulae) or parchment (membranae) of another, the material was considered the principal, and of course the writing belonged to the owner of the paper or parchment. If a man painted a picture on another man's wood (tabula) or whatever the materials might be, the painting was considered to be the principal (tabula picturae cedit). The principle which determined the acquisition of a new property by accessio was this — the intimate and inseparable union of the accessory with the principal.
Accordingly, there might be accessio by pure accident without the intervention of any rational agent. If a piece of land was torn away by a stream from one man's land and attached to the land of another, it became the property of the man to whose land it was attached to, after it was firmly attached to it, but not before. This must not be confounded with the case of Alluvio.
The person who lost his property by accessio had as a general rule a right to be indemnified for his loss by the person who acquired the new property. The exceptions were cases of mala fides (bad faith).
The term accessio is also applied to things which are the products of other things, and not added to them externally as in the aforementioned cases. Every accessio of this kind belongs to the owner of the principal. The produce of a beast, the produce of a field and of a tree, belongs to the owner. In some cases a man may have a right to the produce (fructus) of a thing, though the thing belongs to another. (Usus fructus).
The term accessiones was also applied to those who were certain or bound for others, as fidejussores (Confusio)
- This article is copied from Smith, W. (1878). A dictionary of Greek and Roman antiquities. London: J. Murray, a work that is now in the public domain. This source cites as its sources Krüger, P., Mommsen, T., Schöll, R., & Kroll, W. (1954). Corpus iuris civilis. Berolini: Apud Weidmannos; Gaius, Commentary II; and Digest of Ustinian