I feel a lot of people misunderstand DHS' role in the United States. They are a law enforcement agency (Like we really needed another one though) that has a broad responsibility. Those ICE (Most likely HSI) guys really do a whole lot for the U.S., and unfortunately a lot are in harms way here at home.
I don't think they need full auto, there's a special situation that requires a magazine to get dumped all at once, and those ain't happening in LA.