Rich Wales goes into more detail and with legal references. Although his site has not been updated since 2011, the fundamental information remains useful and clearly presented. One caveat is that it is U.S.-specific—it is very informative for Americans, less so if you’re not interested in U.S. citizenship.
Here are TDT’s answers to questions that seem to come up often about dual citizenship.
• What is dual citizenship?
Dual citizenship means holding the citizenship of two countries at the same time. I use “dual citizenship” to mean multiple citizenship—these answers are the same even if a person holds three or more citizenships at the same time.
Dual citizenship is not a special status in itself. A citizen of country A is just like any other citizen of A, and if she is also a citizen of B, then country B will treat her just like any other citizen. There is no world authority that administers dual citizenship, and no form to fill out for it.
• How does this happen?
Every country has its own rules defining who is and is not its citizen. Those rules are made independently by each country, regardless of other countries’ rules. When, for any number of reasons, the rules of country A define you as its citizen and the rules of country B also define you as its citizen, citizenships overlap, and you have both.
• Surely “where are you from?” isn’t a difficult question—a person can only be born in one place.
True, but it’s not only birth that leads to citizenship, and it’s not only where you are born that can count:
1. A person can gain citizenship by birth in several ways. Some (not most) countries define you as a citizen if you were born there (U.S.A.). Some define you as a citizen if you were born there, but with caveats (your parents have to be settled there and not just visiting, for example) (Britain). And some say that you are born with their citizenship because your parents or even grandparents were citizens, even though you were born somewhere else. In this last example, you could be born a dual citizen—if you have an American mother who’s settled in Britain, married to your British father, you have both citizenships from birth.
2. A person can also gain citizenship later in life, by naturalizing. If you immigrate to a new country and settle there, eventually you may be eligible to apply for citizenship. Unless your country of citizenship by birth has a law taking citizenship away if you become the citizen of another country (a few countries do have this rule), you are now a citizen of both. Even if your new country (the U.S. for example) requires an oath saying that you are no longer a citizen of any other countries, in practice, your old country may not recognize this oath as having any value (why would it care about U.S. citizenship laws?) In this case, you are still a citizen of both countries.
• But that’s wrong, isn’t it? I mean how can you be loyal to two different countries? What if they went to war with one another?
Whether it’s wrong or not is a personal decision and depends what loyalty means to you. It also depends on how likely the two countries are to go to war with each other, and what the practical effect would be. For some people, dual citizenship might be an advantage, for others a disadvantage. In today’s world, many people retain strong attachments to one country—family, grew up there, etc.—but actually live in another country because of their work or because their spouse is from there. They want to be full participants in the society where they actually live, without giving up their roots in a different society.
In terms of personal identity, what nationality means to you and how you identify will depend on a lot of things, not just citizenship. An Italian–American may qualify for Italian citizenship and be proud of her Italian heritage, while still being American! This is an easier concept for immigrant-based cultures, like Canada and the U.S., than it is in Old World cultures.
• Still, you’re really only one or the other, right?
Legally, each country of your citizenship will treat you only as its citizen. So if you’re both an American and a British citizen, America will regard you as American alone (like any other American citizen), and Britain will regard you as British alone. You can’t go to the British embassy in America and claim help if you violate American laws, for example. As a general rule, if you are in a country you’re a citizen of, that country’s laws take priority—it has a stronger claim on you. If you’re in a third country, again as a general rule, you identify yourself by the passport you use to enter that country.
• So it turns out I’m eligible for another citizenship. What should I do?
Find out whether holding the other citizenship (B) will cause conflicts with the country you’re a citizen of now (A). Is A one of those countries that takes away your citizenship if you acquire another? Will B require you to do something onerous, like military service in the old country? If there are no such pitfalls, decide whether the advantages of dual citizenship (see below) outweigh the possible disadvantages. Once you decide what’s right for your case, there is usually an application process before you actually acquire the other citizenship—either by naturalizing or by proving you’re entitled to it by birth.
• Right, so I’m a dual citizen now. Do I need to get a passport from my new country, and travel with it?
Not necessarily. A passport is just a travel document, not citizenship. People with no plans to travel outside the country they live in often don’t have a passport at all. On the other hand, if you have ties to another country where you might have to travel at short notice—relatives there, for instance—it’s wise to keep an up-to-date passport at all times.
• So which passport should I use?
This depends on your travel requirements. U.S. law, for example, requires anyone who is a U.S. citizen to travel to and from the U.S. with a U.S. passport (regardless of any other citizenships that person may have). So an American who lives or travels abroad really needs an American passport. If your country has a similar requirement and you plan to travel there, then get a passport from that country. Usually, a passport is also the best way to establish that you’re entitled to live and work in that country and stay indefinitely, without any visa restrictions. But not always. British citizens, for example, are not required to travel on British passports, and can get a certificate in another passport showing that they have the “right of abode” in Britain. While this certificate is more expensive than a passport, and doesn’t confer the advantages of having a European Union passport in the rest of the EU, it is much quicker and less complicated to apply for than a first-time British passport.
• What are the advantages of dual citizenship?
Dual citizenship means you have the right to live, work, and stay indefinitely in more than one country, as well as to travel freely there. Unlike a foreign visitor, a citizen has the right to enter a country, and cannot be turned away at the border. For more on traveling with two passports, see "The A to B of traveling with two passports," below.
Quite apart from travel, citizenship also entitles you to participate fully in the life of a country, and if you have ties with more than one country, dual citizenship identifies you with both. For instance, it may give you the right to vote in the country where you live, as well as in elections “back home.” Citizenship means that you belong in a country. Unlike permanent residence or other visa status, it cannot usually be taken away, even if you live outside the country for years. (There can be exceptions, if you obtained the citizenship through fraud or committed a crime in the process, for example.)
• What are the possible disadvantages?
Some countries’ rules do cause conflicts, as already mentioned. Some countries restrict security clearances in the case of people with other citizenships; dual citizenship would therefore be a disadvantage if you wanted to apply for certain jobs. And, if you try for high office, you could have a political problem if your opponents tried to characterize you as disloyal (politicians not being constrained by the facts). Michaëlle Jean, the former Governor General of Canada, was criticized for being a dual citizen of Canada and France; her political opponents portrayed her French citizenship unfavorably, and eventually, she renounced it. (Most countries have a formal procedure for renouncing citizenship, rather than your automatically losing it. This is true for the U.S.—it is actually quite difficult for someone born with American citizenship to lose it, even if he wanted to.)
Also, be aware that obligations of one citizenship don’t go away just because you acquire another. The U.S. infamously requires its citizens to file tax forms every year, no matter what other citizenships they have or how long they’ve lived outside the U.S.
• I still don't get it. I get that some people may identify with two nationalities, but is there any justification for claiming a second citizenship, just because you are entitled to it?
This comes up in the media, often in regard to athletes who compete for a country other than the one they were born in. Sometimes this is politically dubious. Americans, for example, are happy to welcome athletes who defected from former communist bloc nations, but less happy to see athletes from the U.S. now competing for Russia.
However, there are circumstances where a second nationality, even if you wouldn’t otherwise claim it, can be of immense practical help. Suppose you lived in South Africa under apartheid, and because of ancestry, you were entitled to claim Irish citizenship. You might take the chance to start a new life in Ireland, rather than live under a system you found intolerable—even though you were still a proud South African. Or, although you are a proud Canadian, you have a British spouse, and are living together in Britain. In order to come and go without being subject to British immigration controls, you might choose to claim citizenship once entitled to it, without ever identifying as British.
These decisions don’t always make sense to others or to the wider public, but for personal reasons, they do. Wanting to live under a different type of government, or being married to a citizen, are convincing reasons to desire nationality. Those who disagree have perhaps always taken their own system for granted, or never fallen in love with a foreigner.
Enjoy your citizenship(s), whatever it or they may be. Enjoy your travels.