A question from a client today prompted me to write an updated version of a 2009 blog posting.
Many people wonder whether the US allows dual citizenship, and are surprised to learn that it is allowed. Specifically, people often ask if they can retain their original, non-US, citizenship and still become US citizens. The short answer is "yes" - IF the other country allows dual citizenship. For instance, I have dual US and Irish citizenship, since I was born and raised in Ireland and am a naturalized US citizen.
Based on the US State Department regulation on dual citizenship, the US Supreme Court stated that dual citizenship is a "status long recognized in the law” and that a person may have and exercise rights of nationality in two countries and be subject to the responsibilities of both. The mere fact he asserts the rights of one citizenship does not without more mean that he renounces the other. Kawakita v. U.S., 343 U.S. 717 (1952).
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.
Nevertheless, under US law, it is perfectly legal to be a citizen of the US and of another country. When you enter the US, however, you must use your US passport.
For information on which countries allow dual citizenship, please check local country laws or your country's consulate.
Elaine Martin has been practising US and global immigration law since 1997. She is an immigrant herself (from Ireland), so has a special understanding of the legal and emotional challenges involved in relocating to a new country.