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.

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