A federation (from Latin: ''foedus'', gen.: ''foederis'', "covenant"), also known as a federal state, is a political entity characterized by a union of partially self-governing states or regions under a central (federal) government. In a federation, the self-governing status of the component states, as well as the division of power between them and the central government, are typically constitutionally entrenched and may not be altered by a unilateral decision of either party, the states or the federal political body.〔It is often argued that federal states where the central government has 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 infringe 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, are not truly federal states.〕
The governmental or constitutional structure found in a federation is known as federalism. It can be considered the opposite of another system, the unitary state. Germany, with sixteen ''Bundesländer'', is an example of a federation, whereas neighboring Austria and its ''Bundesländer'' was a unitary state with administrative divisions that became federated, and neighboring France by contrast has always been unitary.
Federations may be multi-ethnic and cover a large area of territory (e.g. Russia, the United States, or India), although neither is necessarily the case. The initial agreements create a stability that encourages other common interests, reduces differences between the disparate territories, and gives them all even more common ground. At some time this is recognized and a movement is organized to merge more closely. At other times, especially when common cultural factors are at play such as ethnicity and language, some of the steps in this pattern are expedited and compressed.
The international council for federal countries, the Forum of Federations,〔(Forum of Federations )〕 is based in Ottawa, Ontario, Canada. It helps share best practices among countries with federal systems of government, and currently includes nine countries as partner governments.
Several ancient chiefdoms and kingdoms, such as the 4th-century BC League of Corinth, Noricum in Central Europe, and the Haudenosaunee Confederation in pre-Columbian North America, could be described as federations or confederations. The Old Swiss Confederacy was an early example of formal non-unitary statehood.
Several colonies and dominions in the New World consisted of autonomous provinces, transformed to federal states upon independence (see Spanish American wars of independence). The oldest continuous federation, and a role model for many subsequent federations, is the United States. Some of the New World federations failed; the Federal Republic of Central America broke up into independent states ten years after its founding. Others, such as Argentina and Mexico, have shifted between federal, confederal, and unitary systems, before settling into federalism. Brazil became a federation only after the fall of the monarchy (see States of Brazil), and Venezuela became a federation after the Federal War. Australia and Canada are also federations.
Germany is another nation-state that has switched between confederal, federal and unitary rules, since the German Confederation was founded in 1815. The North German Confederation and the Weimar Republic were federations.
Founded in 1922, the Soviet Union was formally a federation of Soviet Republics, Autonomous republics of the Soviet Union and other federal subjects, though in practice highly centralized under the Government of the Soviet Union. The Russian Federation has inherited a similar system.
Nigeria, Pakistan, India and Malaysia became federations on or shortly before becoming independent from the British Empire.
The Forum of Federations was established in 1999.
In some recent cases, federations have been instituted as a measure to handle ethnic conflict within a state, such as Bosnia and Herzegovina, and Iraq since 2005.
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