To who ? The Iraqi city police that are busy with the day to day function of maintaning law in order in a big city? If you go with the assumption that he was picked up for breaking a local law by the Iraqi police and not anything directed by the U.S. he would have been picked up locally by the police and detained locally by the same local police.

At what point does his name ring a bell to the Iraqi police? They just know who Nick Berg is? so they pick him up for wandering arround after curfew or carrying a gun. Isn't it a local matter? Again, why wasn't he charged and why is the only story that we are hearing is that he was held for his own protection?

My point being that his aprehention and detention absolutely had to be under the direction of U.S. intelligence at one point or another because they are the only ones that would see the need for him to be interviewed by the FBI or other intelligence services.