The 6th Border Jaegers were originally part of the 6th UMFL Border Legion, an assortment of regiments operating in the Arietis Arm, under the direction of the Union Custodian for the area, Matthias Stone.
The Jaegers, a semi-autonomous regiment based in the Lappi system, were a reaction force under Stone's personal control. Stone, who became known to history as the Bedlam Butcher gave the Jaegers increasingly distasteful orders and assignments over the course of nearly a decade, culminating in the Greenhouse Riots on Acanthus.
Working in concert with another Lappi regiment serving on Acanthus, the Jaegers bode their time, and then "vanished" after being ordered to open fire on rioters in the central city Spinos. Their frames were eventually discovered lining the road leading to the city's main gates like an honor guard, pistons spiked to ensure they could not be used.
Stone flew into a rage, but by the time that translated into rational action, they'd already made transit out of the system.
As Stone's actions have been considered suspect at best by the Solar Union, they have never taken definitive action against the rebellious Jaegers, though rumor has it that certain officials have worked in "unofficial" capacities against them.
Much reduced in size, as the entire regiment did not choose the same path, the 6th Border Jaegers now hire out their services without regard to politics. Even the Union now employs them with the same frequency as any other organization.