It recently came to my attention how gruesomely Russian POW's during world war 2 in a camp nearby were treated. When digging around about this I started to wonder whether these POW camps were under of the Wehrmacht or the SS (like the concentration camps), because if they were under control of the Wehrmacht the treatment would be an enormous warcrime on their part. I personally am talking about the Emslandlager in particular but any other POW camps that can serve as an example will do. Thanks in advance!
German POW camps, except for initial transitional camps near the front, were under the administration of the General Armed Forces Office (Allgemeines Wehrmachtsamt or AWA), which was indeed part of the Wehrmacht, and the Wehrmacht was responsible for the crimes committed in the camps.
After the failed assassination attempt on Hitler on July 20, 1944, command of the military administration of Germany (the so-called Ersatzheer, or Replacement Army), including the POW camps, was transferred to Himmler, who on October 1 placed an SS officer, Gottlob Berger, in charge of the administration of POW camps overall.
On the level of individual camps however, the existing Wehrmacht-led administrations were left in place, and this change didn't really cause any major immediate differences in treatment of POWs either.
A good source that's available online is Geck, S. (1998), Das deutsche Kriegsgefangenenwesen 1939-1945 (master's thesis). Johannes Gutenberg-Universität Mainz, page 12-31.
It's not the newest source, but at least this section deals mostly with the formal organizational and command structure of the camps which isn't really subject to changes in interpretation over time.