http://canada.usembassy.gov/consular_services/dual-citizenship.html
DUAL CITIZENSHIP
The concept of dual nationality means that a person is a citizen of two countries at the same time. Each country has its own citizenship laws based on its own policy. Persons may have dual nationality by automatic operation of different laws rather than by choice. For example, a child born in a foreign country to U.S. citizen parents may be both a U.S. citizen and a citizen of the country of birth.
The U.S. Government acknowledges that dual nationality exists but does not encourage it as a matter of policy because of the problems it may cause. Claims of other countries on dual national U.S. citizens may conflict with U.S. law, and dual nationality may limit U.S. Government efforts to assist citizens abroad. The country where a dual national is located generally has a stronger claim to that person's allegiance.
However, dual nationals owe allegiance to both the United States and the foreign country. They are required to obey the laws of both countries. Either country has the right to enforce its laws, particularly if the person later travels there. Most U.S. citizens, including dual nationals, must use a U.S. passport to enter the United States. Dual nationals may also be required by the foreign country to use its passport to enter that country. Use of the foreign passport does not put into jeopardy your U.S. citizenship. Most countries permit a person to renounce or otherwise lose citizenship.
A U.S. citizen may acquire foreign citizenship by marriage, or a person naturalized as a U.S. citizen may not lose the citizenship of the country of birth. U.S. law does not mention dual nationality or require a person to choose one citizenship over another. Also, a person who is automatically granted another citizenship does not risk losing U.S. citizenship. However, a person who acquires a foreign citizenship by applying for it may lose U.S. citizenship. In order to lose U.S. citizenship, the law requires that the person must apply for the foreign citizenship voluntarily, by free choice, and with the intention to give up U.S. citizenship. Intent can be shown by the person's statements or conduct.
If you are a U.S. citizen who has acquired or plans to acquire Canadian citizenship, and you intend to relinquish your U.S. citizenship or wish to relinquish your U.S. citizenship, please discuss with the U.S. Embassy or Consulate the procedures necessary to formalize this. There will be a US$450 fee to document formal renunciation of U.S. citizenship. More information relating to the loss of citizenship is on this Travel.State.Gov information sheet. In addition, please review this page, regarding the making of a citizenship claim.
Information on losing foreign citizenship should be obtained from the foreign country's Embassy and Consulates in the United States or Canada.
Difference Between Nationality and Citizenship
from http://www.differencebetween.net/miscellaneous/difference-between-nationality-and-citizenship/
Nationality and citizenship are two terms that are sometimes used interchangeably. Some people even use the two words ‘“ citizenship and nationality — as synonyms. But this is not true and they differ in many aspects.
First of all let’s see what nationality means. In simple words, nationality can be applied to the country where an individual was born. Then what does citizenship stands for? It is a legal status, which means that an individual has been registered with the government in some country.
An individual is a national of a particular country by birth. Nationality is got through inheritance from his parents or it be called a natural phenomenon. On the other hand an individual becomes a citizen of a country only when he is accepted into that country’s political framework through legal terms.
Elaborating the two words, an individual born in India, will be having Indian Nationality. But he may have an American citizenship once he has registered with that country.
Well, No one will be able to change his nationality but one can have different citizenship. An Indian can have an American or Canadian citizenship but he cannot change his nationality. Another example is that people of the European Union may have European Union Citizenship but that person’s nationality does not change.
Coming to citizenship, some nations also confer honorary citizenship to individuals. But no country can confer honorary nationality on any one as his birthplace cannot be changed.
Nationality can be described as a term that refers to belonging to a group having same culture, traditions history, language and other general similarities. On the other hand, citizenship may not refer to people of the same group. For example, an Indian and may be having a US citizenship but he will not be belonging to the same group as that of the American nationals.
Summary
1. Nationality can be applied to the country where an individual has been born. Citizenship is a legal status, which means that an individual has been registered with the government in some country.
2. Nationality is got through inheritance from his parents or it be called a natural phenomenon. On the other hand an individual becomes a citizen of a country only when he is accepted into that country’s political framework through legal terms.
3. No one will be able to change his nationality but one can have different citizenship.
Read more: Difference Between Nationality and Citizenship
Difference Between
Nationality vs Citizenship http://www.differencebetween.net/miscellaneous/difference-between-nationality-and-citizenship/#ixzz3BEoYV5ic
泣血长文:不承认双重国籍的三大恶果