In a federation, the division of power between federal and regional governments is usually outlined in the constitution. It is in this way that the right to self-government of the component states is usually constitutionally entrenched. Component states often also possess their own constitutions which they may amend as they see fit, although in the event of conflict the federal constitution usually takes precedence. In almost all federations the central government enjoys the powers of foreign policy and national defense. Were this not the case a federation would not be a single sovereign state, per the UN definition. Notably, the states of Germany retain the right to act on their own behalf at an international level, a condition originally granted in exchange for the Kingdom of Bavaria's agreement to join the German Empire in 1871. Beyond this the precise division of power varies from one nation to another. The constitutions of Germany and the United States provide that all powers not specifically granted to the federal government are retained by the states. The Constitution of some countries like Canada and India, on the other hand, state that powers not explicitly granted to the provincial governments are retained by the federal government. Much like the US system, the Australian Constitution allocates to the Federal government (the Commonwealth of Australia) the power to make laws about certain specified matters which were considered too difficult for the States to manage, so that the States retain all other areas of responsibility. Under the division of powers of the European Union in the Lisbon Treaty, powers which are not either exclusively of European competence or shared between EU and state are retained by the constituent states. In Canada, the provincial governments derive all their powers directly from the constitution. In contrast, the territories are subordinate to the federal government and are delegated powers by it. Where every component state of a federation possesses the same powers, we are said to find 'symmetric federalism'. Asymmetric federalism exists where states are granted different powers, or some possess greater autonomy than others do. This is often done in recognition of the existence of a distinct culture in a particular region or regions. In Spain, "historical communities" such as Navarre, Galicia, Catalonia, and the Basque Country have more powers than other autonomous communities, partly to deal with their distinctness and to appease nationalist leanings, partly out of respect of privileges gra
ted earlier in history. It is common that during the historical evolution of a federation there is a gradual movement of power from the component states to the centre, as the federal government acquires additional powers, sometimes to deal with unforeseen circumstances. The acquisition of new powers by a federal government may occur through formal constitutional amendment or simply through a broadening of the interpretation of a government's existing constitutional powers given by the courts. Usually, a federation is formed at two levels: the central government and the regions (states, provinces, territories), and little to nothing is said about second or third level administrative political entities. Brazil is an exception, because the 1988 Constitution included the municipalities as autonomous political entities making the federation tripartite, encompassing the Union, the States, and the municipalities. Each state is divided into municipalities (municipios) with their own legislative council (camara de vereadores) and a mayor (prefeito), which are partly autonomous from both Federal and State Government. Each municipality has a "little constitution", called "organic law" (lei organica). Mexico is an intermediate case, in that municipalities are granted full-autonomy by the federal constitution and their existence as autonomous entities (municipio libre, "free municipality") is established by the federal government and cannot be revoked by the states' constitutions. Moreover, the federal constitution determines which powers and competencies belong exclusively to the municipalities and not to the constituent states. However, municipalities do not have an elected legislative assembly. Federations often employ the paradox of being a union of states, while still being states (or having aspects of statehood) in themselves. For example, James Madison (author of the US Constitution) wrote in Federalist Paper No. 39 that the US Constitution "is in strictness neither a national nor a federal constitution; but a composition of both. In its foundation, it is federal, not national; in the sources from which the ordinary powers of the Government are drawn, it is partly federal, and partly national..." This stems from the fact that states in a federation maintain all sovereignty that they do not yield to the federation by their own consent. This was reaffirmed by the Tenth Amendment to the United States Constitution, which reserves all powers and rights that are not delegated to the Federal Government as left to the States and to the people.