根据美国《移民和国籍法》(INA)第101(a)(22)条规定，“‘美国国民’指(A)美国公民，或(B)虽然不是美国公民，但是要 ** 效忠美国的人。”因此，美国公民也是美国国民。非公民国籍仅适用于父母非美国公民，而出生于美属萨摩亚或斯文斯岛的个人。双重国籍是指同时是两个国家国民的人。每个国家根据其自身政策，都有其自己的国籍法。人们可以通过自动形式，而非选择形式，拥有双重国籍。例如：美国国民的父母生在国外的小孩既可以是美国国民，也可以是出生所在国的国民。
一个美国国民可以通过结婚获得国外国籍，或者一个外国人可以入美国籍而无需放弃出生所在国家的国籍。美国法律并未提到双重国籍或要求一个人在美国国籍和其他国籍之间二选一。而且，一个被自动赋予另外一个国籍的人并不会有失去美国国籍的风险。然而，如果一个人要申请获得国外国籍可能要放弃美国国籍。如果要放弃美国国籍，法律规定该放弃人必须主动申请，自由选择国外国籍，并且有放弃美国国籍的意图。
该意图可以通过申请人的声明或行为来 呈现。美国政府承认双重国籍的存在，但是因为双重国籍可能会产生某些问题，并不在政策上鼓励。如：持美国国民身份的双重国籍所有人，在另一国家的要求可能会与美国法律相冲突;而且，双重国籍可能会限制美国政府为帮助其海外国民而作出的努力。双重国籍的另一个国家通常对双重国籍拥有人的忠诚度有更高的要求。
然而，双重国籍所有人需对美国和另一国家同时效忠。他们被要求遵守两个国家的法律。任一国家都有权来实施其法律，特别是该所有人刚到达这个国家。大多数美国国民，包括双重国籍持有人，必须在进入和离开美国时使用美国护照。双重国籍持有人可能也会被外国要求在进入和离开该国家时使用该国家的护照。使用国外护照并不会危及美国国籍。大多数国家都允许一个人放弃国籍。
放弃国外国籍的信息可以在驻美的国外使馆和领事馆获得。美国人也可以通过美国在海外的大使馆和领事馆通过恰当形式放弃。
美国官方原文如下：
Dual Nationality
Section 101(a)(22) of the Immigration and Nationality Act (INA) states that “the term ‘national of the United States’ means (A) a citizen of the United States, or (B) a person who, though not a citizen of the United States, owes permanent allegiance to the United States.” Therefore, U.S. citizens are also U.S. nationals. Non-citizen nationality status refers only individuals who were born either in American Samoa or on Swains Island to parents who are not citizens of the United States. The concept of dual nationality means that a person is a national of two countries at the same time. Each country has its own nationality 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. national parents may be both a U.S. national and a national of the country of birth.
A U.S. national may acquire foreign nationality by marriage, or a person naturalized as a U.S. national may not lose the nationality of the country of birth. U.S. law does not mention dual nationality or require a person to choose one nationality or another. Also, a person who is automatically granted another nationality does not risk losing U.S. nationality. However, a person who acquires a foreign nationality by applying for it may lose U.S. nationality. In order to lose U.S. nationality, the law requires that the person must apply for the foreign nationality voluntarily, by free choice, and with the intention to give up U.S. nationality.
Intent can be shown by the person's statements or conduct. The U.S. Government recognizes 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. nationals may conflict with U.S. law, and dual nationality may limit U.S. Government efforts to assist nationals 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. nationals, including dual nationals, must use a U.S. passport to enter and leave the United States. Dual nationals may also be required by the foreign country to use its passport to enter and leave that country. Use of the foreign passport does not endanger U.S. nationality. Most countries permit a person to renounce or otherwise lose nationality.
Information on losing foreign nationality can be obtained from the foreign country's embassy and consulates in the United States. Americans can renounce U.S. nationality in the proper form at U.S. embassies and consulates abroad.
http://travel.state.gov/content/travel/english/legal-considerations/us-citizenship-laws-policies/citizenship-and-dual-nationality/dual-nationality.html
本文严禁转载，如需转载，请注明转自津桥移民后期中心移民文案靳闻琼原创。审核人：李晓丽
