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.
Accessio has continued relevance in present times, partly due to the adoption of Roman law principles by legal systems across Europe, Africa, Asia and South America, primarily civilian legal systems.
Legal systems across the modern world continue to employ a form of accessio.
Modern legal systems go further when describing accession, including all circumstances where property has been increased physically but the Roman law concept relates to merger of an accessory and principal alone.
[3] Further reading on contemporary usage of accesio in modern states can be found in (L. van Vliet, ‘Accession of Movables to Land’ (2002) 6 Edin LR 67).