Dual citizenship (being a citizen of two nations) is by far the most common type of multiple citizenship, but nothing in international law prevents individuals from establishing citizenship in more than two countries. Some countries prohibit their citizens from establishing citizenship in another country or only permit it in certain circumstances or for certain countries. Other countries place no restrictions upon citizens wishing to become citizens of other lands.
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Each country has different requirements for citizenship, as well as different policies regarding dual citizenship. An Australian study estimated that 4–5 million Australians (up to 25% of the Australian population) had dual citizenship in 2000. An estimated sixty percent of Swiss nationals living abroad in 1998 were dual citizens. Approximately 89 countries in the world officially allow some form of dual or multiple citizenship. In the United States it is estimated that millions of Americans are also citizens of other countries. In spite of very restrictive German laws, there was an estimated in 1994 1.2 million dual citizens with German citizenship.
There are some legal issues about dual citizenship and government services. For example, an American citizen with a second nationality and passport may have issues getting a security clearance if they prefer to use the non-American passport or work within the United States government.
While multiple citizenship can be helpful as the individual can carry two or more passports, it is prudent to realize that each citizenship carries responsibilites, such as the risk of conscription or "the draft", as well as pledging allegiance to more than one state, and having to observe travel restrictions, embargoes and sets of laws issued by multiple governments governing one's behavior domestically and while travelling abroad. Also, a drawback peculiar to a few countries such as the US, citizens are the obligated to pay taxes in both the country of origin and the actual country of residence.
The numbers are large and increasing. Millions of people in the world are presently citizens of more than one country. The number of multiple citizens is going to increase rapidly as people become ever more mobile, living, marrying and having children in multiple countries over the course of their lives.
It brings important personal opportunities and responsibilities. As a citizen of a country, you have the opportunity to live there, go to school, work, get medical care, have children, buy property, and retire. There may be agreements to allow freedom of movement to other countries, as in the European Union. There may also be responsibilities connected with citizenship, such as potential military service.
Example 1: A person born in Canada, to a Canadian citizen and an American citizen would have Canadian citizenship by birth, and may also have US citizenship, depending on certain circumstances (the parents' marital status, date of the child's birth, and whether the US citizen parent has met certain physical presence requirements). If the requirements have been met, then the child would also be a US citizen, and therefore would have dual citizenship.
Example 2: A person may be born in the United States to American parents, they may end up moving to the United Kingdom, and after five years of legal residence(or three years if married to a UK citizen. This person may become a UK citizen, therefore, this person will hold dual UK/US citizenship.
Example 3: A child is born in Canada to British parents. The child is entitled to dual citizenship at birth. Lex sanguinis applies for his British citizenship through his blood relationship with his parents, and Lex soli applies for his Canadian citizenship because of his birth on Canadian soil.
- British nationality law
- Foreign-born Japanese
- Indian citizenship law (incl. dual citizenship law)
- Jus soli
- Jus sanguinis
- Dual and Multiple Citizenship
- Citizenship Laws of the World from the United States Office of Personnel Management Investigations Service (PDF)