Law enforcement
From Halopedia, the Halo wiki
The Civilian Security Forces are police units used on the colonies of the UNSC. They use weaponry like the M90A Law Enforcement, M7/Caseless Submachine Gun, M6A Handgun,and M6B Handgun instead of assault and battle rifles. During the Battle of Harvest, CSF constables were on foot patrol at the Gladsheim mall. They wore helmets and riot plating, and were armed with stun devices and plastic shields. Two other constable named Finn and Lars were the personal body guards of Governor Thune. [1] It is possible that at the Battle of Voi groups of Civilian Security Forces fought alongside Marine strike groups.
C.S.F. Sub-Agencies
Sources
Halo: Contact Harvest, page 319
Halo: Contact Harvest, page 320