voluntarily bind themselves by treaty to a supranational organization, such as a continental union. In the case of the European Union member-states, this is called "pooled sovereignty". Another example of shared and pooled sovereignty is the Acts of Union 1707 which created the unitary state now known as the United Kingdom. It was a full economic union, meaning the Scottish and English systems of currency, taxation and laws regulating trade were aligned. Nonetheless, Scotland and England never fully surrendered or pooled all of their governance sovereignty; they retained many of their previous national institutional features and characteristics, particularly relating to their legal, religious and educational systems. In 2012, the Scottish Government, created in 1998 through devolution in the United Kingdom, negotiated terms with the Government of the United Kingdom for the 2014 Scottish independence referendum which resulted in the people of Scotland deciding to continue the pooling of its sovereignty with the rest of the United Kingdom. Nation-states A community of people who claim the right of self-determination based on a common ethnicity, history and culture might seek to establish sovereignty over a region, thus creating a nation-state. Such nations are sometimes recognised as autonomous areas rather than as fully sovereign, independent states. Federations In a federal system of government, sovereignty also refers to powers which a constituent state or republic possesses independently of the national government. In a confederation, constituent entities retain the right to withdraw from the national body and the union is often more temporary than a federation. Different interpretations of state sovereignty in the United States of America, as it related to the expansion of slavery and fugitive slave laws, led to the outbreak of the American Civil War. Depending on the particular issue, sometimes both northern and southern states justified their political positions by appealing to state sovereignty. Fearing that slavery would be threatened by results of the 1860 presidential election, eleven slave states declared their independence from the federal Union and formed a new confederation. The United States government rejected the secessions as rebellion, declaring that secession from the Union by an individual state was unconstitutional, as the states were part of an indissoluble federation. Sovereignty vs. military occupation In situations related to war, or which have arisen as the result of war, most modern scholars still commonly fail to distinguish between holding sovereignty and exercising military occupation. In regard to military occupation, international