The theory of Montesquieu, which defends the separation of powers was implemented in many constitutions around the world. It was implemented in the US Constitution, because the founding fathers considered that the American states sufferd abuse from the powers of the monarchy and parlamentarism. The constitution limits the powers of the federal government and balances the powers, which are:
Legislative - makes law
Executive - executes and forces the law
Judiciary - interprets and applies the law in the name of the state.
