The dual elements in conveyance of res mancipi created circumstances where physical possession could be effected, while slovenly performance of the mancipation had created a "vice of the title" or title defect. A mechanism called "uscapacion" (usucapio "taking by use") could be applied to cure the defect and resolve disputes of actual and technical right; or "equitable" and "legal" title. In order to have the benefit of usucapion, it was necessary that actual adverse possession or prescription was begun in good faith, with belief on the part of the possessor that he was lawfully acquiring the property. Basically, the rule of the actio Publiciana stated that things that had been uninterruptedly possessed for a certain period became the property of the possessor, usually by two years at the most. (Longa possessio parit jus possidendi, et tollit actionem vero domino. = Long possession produces the right of possession, and takes away from the true owner his action. Co. Litt. 110.)
Under old Roman law, ownership or proprietary rights were distributed between rights Quiritarian (iure Quiritium or legal title) and Bonitarian (equitable or possessory in bonis holding.) Until fused by Justinian reform, Roman Civil Law and Roman Equity (remedies which had their source in the Roman Praetor's Edict,) were separately administered by the same court. Through the exceptio rei venditae et traditae, the magistrate could refuse to grant the "legal" owner those Real Actions (vindicatio,) and pleas under Law that would allow him to recover property that belonged in equity (possession) to another. This could be used to give an immediate right of property to the person who had acquired a Res Mancipi by mere delivery, without waiting for the ripening of usucapion.
JUS DUPLICATUM, property, title. When a man has the possession as well as the property of anything, he is said to have a double right, jus duplicatum. Bract. 1. 4, tr. 4, c. 4 2 Bl. Com. 199. (see allodial.)
--------------> To "Public Lands" Section