The Department of Justice is the world's largest law office and the chief enforcer of federal laws. It's purpose is to enforce the law and defend the interests of the United States according to the law; to ensure public safety against threats foreign and domestic; to provide federal leadership in preventing and controlling crime; to seek just punishment for those guilty of unlawful behavior; and to ensure fair and impartial administration of justice for all Americans.

The Department of Justice was empowered to handle all criminal prosecutions and civil suits in which the United States had an interest. To assist the Attorney General, the 1870 Act also created the Office of the Solicitor General, who represents the interests of the United States before the U.S. Supreme Court.