A
Latin phrase meaning literally "of one's own right." In English, it is used in
law to mean "legally
competent to
manage one's affairs or assume
responsibility." One is usually
sui juris if they are of
legal age, a free (non-slave) person, and of
sound mind (one source also mentions
bankruptcy as preventing a person from being considered
sui juris) so all
adults are presumed to be
sui juris unless specifically proved otherwise. For a
contract to be valid, the person making it has be to be
sui juris.
The phrase is also used in another context; discussions of the Catholic church may refer to "churches sui juris," churches with a distinct community of faithful people and their own hierarchy; the Roman Catholic Church is one church sui juris and certainly the biggest Catholic church, but there are 21 Eastern churches (Coptic, Ethiopian, Armenian, Greek, etc.) which are Catholic (not Eastern Orthodox). Each one "has its own rules, government, liturgy and culturally-influenced way of expressing the faith which all Catholics hold in common."
There is also a musician using the name "Sui Juris" with a homepage for his "reggae-ska" music at
http://artists3.iuma.com/IUMA/Bands/SuiJuris/
Sources:
http://wordsmith.org/awad/archives/0502
http://www.lectlaw.com/def2/s196.htm
http://www.duhaime.org/dict-s.htm
http://members.tripod.com/~Berchmans/suijuris.html
http://members.tripod.com/~Berchmans/eastern.html
http://www.byzantines.net/epiphany/ouridentity.htm