The United Mexican States are a federation whose government is representative, democratic and republican based on a presidential system according to the 1917 Constitution. The constitution establishes three levels of government: the federal Union, the state governments and the municipal governments. According to the constitution, all constituent states of the federation must have a republican form of government composed of three branches: the executive, represented by a governor and an appointed cabinet, the legislative branch constituted by a unicameral congress and the judiciary, which will include a state Supreme Court of Justice. They also have their own civil and judicial codes.