A federation (also called a federal state) is an entity characterized by a union of partially self-governing provinces, states, or other regions under a federal government (federalism). In a federation, the self-governing status of the component states, as well as the division of power between them and the central government, is constitutionally entrenched and may not be altered by a unilateral decision, neither by the component states nor the federal political body without constitutional amendment.
Sovereign power is formally divided between a central authority and a number of constituent regions so that each region retains some degree of control over its internal affairs.
Overriding powers of a central authority theoretically can include: the constitutional authority to suspend a constituent state's government by invoking gross mismanagement or civil unrest, or to adopt national legislation that overrides or infringes on the constituent states' powers by invoking the central government's constitutional authority to ensure "peace and good government" or to implement obligations contracted under an international treaty...