In the 1930s America went through a crime wave caused mostly by illegal traders of alcohol and gangsters. To control this increasing criminality wave, which included murder and armed robbery American government implemented twelve measures which made reforms in the procedures of the law enforcement agency.
Such reforms included, among others, making a federal offense to rob banks so criminals could not keep escaping prosecution by crossing state lines and giving agents of the Bureau of Investigation (or FBI) the authority to carry weapons as well as to make arrests.