Old Law
From Wookieepedia, the Star Wars wiki.
The Old Law was an old Hutt law that allowed for challenges between clan leaders if sufficient provocation had occurred. It allowed for one-on-one mortal combat.
Jabba's great-uncle, Jiliac was killed by Durga in this manner at his Winter Palace, due to Jiliac poisoning Durga's father, Aruk the Hutt.
