"Commissioners cannot be a member of a political party, and cannot, by law, have been an office holder or employee of a political party, or held elective office, for a period of 10 years prior to their appointment, " it added.

BBC: RELATED BBC SITES

Holder, 46, took the oath of office at an installation ceremony in the Justice Department's historic Great Hall.

CNN: AllPolitics - Holder Installed As Deputy Attorney General

Mueller, who previously had a lengthy career in the Justice Department, returned to prosecution after a brief stint in private practice as an attorney in Holder's District of Columbia U.S. Attorney's Office, where he prosecuted homicides.

CNN: Sources: Holder is Obama's choice for attorney general