Criminal Investigation Division
From Halopedia, the Halo wiki
The Criminal Investigation Division (CID) is a UNSC law enforcement agency that operates under UNSC Fleet Command. The CID likely investigates crimes involving UNSC Navy or Marine Corps personnel. During an Office of Naval Intelligence training exercise, Veta Lopis claimed to be with the CID in order to have two ensigns keep Ota Gallo, a Dark Moon Enterprises operative posing as a server, from leaving.