Sui Juris is the name of two separate but semi-related groups led by Open Metal.
The original Sui Juris was a self-styled "reform group" that kidnapped the Cadent Under Mirage and attempted to throw a coup within the Divine Fleet to transfer power away from Seance and Empyrean (thought at the time to be the fleet's last living Divine) to the By-and-By, the fleet's most populous ship. While reflective of actual grievances within the fleet, the Sui Juris coup was engineered by Robin's Song, a New Earth Hegemony soldier and the older brother of Morning's Observation, as a means of destabilizing the Divine Fleet.
After the Miracle of the Mirage and the thwarting of their coup attempt by members of the Beloved, Open Metal went on to lead a ragtag group of mercenaries also known as Sui Juris. This group, compared by Austin to the Chime (protagonists of previous Friends at the Table season COUNTER/Weight), includes Open Metal, the synthetic Beloved Lost alumnus Chiron, and the former Castlerose assassin Armstrong, now in the body of a duck person.