You may be confusing this for POW camp guards often being made up of Ukrainian militia, as well as these same militias conducting anti-partisan sweeps and aiding Einsatzgruppen in the USSR. Initially the Wehrmacht attempted to capitalize on anti-Stalinist and anti-Communist sentiment within the Ukraine and these militia members could often be trusted to conduct rear-echelon duties, such as POW guarding, to free up much needed men for the front.

Of course these pro-fascist militias often treated their charges with exceptional cruelty.