A unitary state is a state governed as one single power in which the central government is ultimately supreme and any administrative divisions (subnational units) exercise only powers that their central government chooses to delegate. The majority of states in the world have a unitary system of government. Of the 193 UN member states, 165 of them are governed as unitary states.
Unitary states are contrasted with federal states (federations) and confederal states (confederation):
* In a unitary state, subnational units are created and abolished, and their powers may be broadened and narrowed, by the central government. Although political power in unitary states may be delegated through devolution to local government by statute, the central government remains supreme; it may abrogate the acts of devolved governments or curtail their powers.
* The United Kingdom is an example of a unitary state. Scotland, Wales, and Northern Ireland have a degree of autonomous devolved power, but such devolved power is delegated by the Parliament of the United Kingdom which may enact laws unilaterally altering or abolishing devolution.
* Many unitary states have no such areas having any degree of autonomy. Subnational areas can not decide any of their own laws. Some examples of such countries are Sweden, Norway〔Svalbard has even less autonomy than mainland. It is directly controlled by the government and has no local rule〕 and Ireland.
* In federal states, by contrast, states or other subnational units share sovereignty with the central government, and the states constituting the federation have an existence and power functions that cannot be unilaterally changed by the central government. In some cases, it is the federal government that has only those powers expressly delegated to it.
* The United States is an example of a federal state. Under the U.S. Constitution, power is shared between the federal government and the U.S. states, with the tenth amendment explicitly stating, "The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people." Many federal states also have unitary lower levels of government; while the United States is federal, the states themselves are unitary under Dillon's Rule – counties and municipalities have only the authority granted to them by the state governments under their state constitution or by legislative acts. For example, in the U.S. State of Connecticut, county government was abolished in 1960.
Devolution (like federation) may be symmetrical, with all subnational units having the same powers and status, or asymmetric, with regions varying in their powers and status.
== List of unitary states ==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』