Sui Juris, in the Roman law, the condition of a person not subject to the Patria Potestas (see FAMILY, Vol. IV. p. 542). The paterfamilias was the only member of a family who was sui juris, all the rest being alieni juris, including sons, unmarried daughters, the wife, and the wives and children of the sons of the paterfamilias. A son or unmarried daughter became sui juris on the death of the paterfamilias. In his father's lifetime a son could only become sui juris by emancipation.
Sui Juris
Chambers's Encyclopaedia, Volume 9: Bound to Swansea, p. 791
Source scan(s): p. 0810