Dual citizenship

Multiple citizenship, also called dual citizenship or multiple nationality or dual nationality, is a person's citizenship status, in which a person is concurrently regarded as a citizen of more than one state under the laws of those states. There is no international convention which determines the nationality or citizen status of a person, which is defined exclusively by national laws, which vary and can be inconsistent with each other. Multiple citizenship arises because different countries use different, and not necessarily mutually exclusive, criteria for citizenship. Colloquial speech refers to people "holding" multiple citizenship but technically each nation makes a claim that this person be considered its national.

Some countries do not permit dual citizenship. This may be by requiring an applicant for naturalisation to renounce all existing citizenship, or by withdrawing its citizenship from someone who voluntarily acquires another citizenship, or by other devices. Some countries do not permit a renunciation of citizenship. Some countries permit a general dual citizenship while others permit dual citizenship but only of a limited number of countries.

Most countries that permit dual citizenship still may not recognize the other citizenship of its nationals within its own territory, for example, in relation to entry into the country, national service, duty to vote, etc. Similarly, it may not permit consular access by another country for a person who is also its national. Some countries prohibit dual citizenship holders from serving in their military, on police forces or holding certain public offices.

Up until the late 19th century, nations often decided who they claimed as their citizens or subjects, and did not recognize any other nationalities they held. Many states did not recognize the right of their citizens to renounce their citizenship without permission, with the feudal theory of perpetual allegiance to the sovereign still common. This meant that people could hold multiple citizenships, with none of their nations recognizing any other of their citizenships. This state of affairs sometimes led to international incidents, notably the War of 1812, triggered by British impressment of American seamen who were alleged to be British subjects into naval service.

In the aftermath of the 1867 Fenian Rising, Irish-Americans who had gone to Ireland to participate in the uprising and were caught were charged with treason, as the British authorities considered them to be British subjects. This outraged many Irish-Americans, to which the British responded by pointing out that, just like British law, American law also recognized perpetual allegiance. As a result, Congress passed the Expatriation Act of 1868, which granted Americans the right to freely renounce their U.S. citizenship. Britain followed suit with a similar law, and years later, signed a treaty agreeing to treat British subjects who had become U.S. citizens as no longer holding British nationality. During this time, diplomatic incidents had also arisen between the United States and several other European countries over their tendency to conscript naturalized American citizens visiting their former homelands. In response, the US government negotiated agreements with various European states known as the Bancroft Treaties, under which the signatories pledged to treat the voluntary naturalization of a former citizen or national with another sovereign nation as a renunciation of their citizenship.

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