Camp commanders like the ones at Rock Island IL and Elmira NY acted as described in this resolution without official sanction. For instance, see The 101st Pennsylvania in the Civil War, Harold B. Birch, page 133.
Lieutenant Colonel William H. Hoffman, the Federal Commissary General of Prisons, ordered a preliminary 20 percent reduction of rations in the Union camps. He then ordered increased guard forces in preparation for further ration cuts. Secretary of War Edwin M. Stanton approved another order by Hoffman to further sharply reduce food, fuel, shelter and clothing of prisoners to levels which Union propagandists claimed were equal to those prevailing in the South. Much of the death and suffering in the Northern prisons was a direct result of this action.Taken from "Civil War Concentration Camps"