From Destinypedia, the Destiny wiki
The City Militia is the volunteer civilian defense force that works alongside the Vanguard to defend The Last City. The group was originally formed during the creation of the The Last City and aided the Guardians in creating the walls around the City. After the Red Legion's attack on the City, many members fled the city, either joining the guardians on the Moon of Titan or heading to the Farm.
The City Militia has manufactured numerous weapons for its both its members and Guardians alike. Their weapons are typically simple in design, utilizing traditional firearm mechanisms. Like the FOTC, their weapons are heavily customizable, and have been utilized and modified by numerous factions.