In this particular case it was done by Rumsfeld. What happened, as I know everybody is aware.... Normally in a situation like that, as soon as the military operations cease, the State Department would go in and start building a government. Colin Powell did have a very extensive plan for building Iraq, but Rumsfeld, through his influence to President Bush, refused to allow that control to go to the State Department. As a result, Berman was sent over, and all the decisions were handled for a long time through the Department of Defense.
In this particular case it ended up being made by Rumsfeld. Normally, I believe it would be done by the State Department.