Multiple citizenship

Multiple citizenship (or multiple nationality) is a person's legal status in which a person is at the same time recognized by more than one country under its nationality and citizenship law as a national or citizen of that country. There is no international convention that determines the nationality or citizenship status of a person, which is consequently determined exclusively under national laws, which often conflict with each other, thus allowing for multiple citizenship situations to arise.
A person holding multiple citizenship is, generally, entitled to the rights of citizenship in each country whose citizenship they are holding (such as right to a passport, right to enter the country, right to work, right to own property, right to vote, etc.) but may also be subject to obligations of citizenship (such as a potential obligation for national service, becoming subject to taxation on worldwide income, etc.).
Some countries do not permit dual citizenship or only do in certain cases (e.g., inheriting multiple nationalities at birth). This may be by requiring an applicant for naturalization to renounce all existing citizenship, by withdrawing its citizenship from someone who voluntarily acquires another citizenship. Some countries permit a renunciation of citizenship, while others do not. Some countries permit a general dual citizenship while others permit dual citizenship but only of a limited number of countries.
A country that allows dual citizenship may still not recognize the other citizenship of its nationals within its own territory (e.g., in relation to entry into the country, national service, duty to vote, etc.). Similarly, it may not permit consular access by another country for a person who is also its national. Some countries prohibit dual citizenship holders from serving in their armed forces or on police forces or holding certain public offices.
Up until the late 19th century, nations often decided whom they claimed as their citizens or subjects and did not recognize any other nationalities they held. Many states did not recognize the right of their citizens to renounce their citizenship without permission because of policies that originated with the feudal theory of perpetual allegiance to the sovereign. This meant that people could hold multiple citizenships, with none of their nations recognizing any other of their citizenships. Until the early modern era, when levels of migration were insignificant, this was not a serious issue. However, when non-trivial levels of migration began, this state of affairs sometimes led to international incidents, with countries of origin refusing to recognize the new nationalities of natives who had migrated, and, when possible, conscripting natives who had naturalized as citizens of another country into military service. The most notable example was the War of 1812, triggered by British impressment into naval service of US sailors who were alleged to be British subjects.
In the aftermath of the 1867 Fenian Rising, Irish-born naturalized American citizens who had gone to Ireland to participate in the uprising and were caught were charged with treason, as the British authorities considered them to be British subjects. This outraged many Irish-Americans, to which the UK responded by pointing out that, just like British law, US law also recognized perpetual allegiance. As a result, Congress passed the Expatriation Act of 1868, which granted Americans the right to freely renounce their US citizenship. The UK followed suit, and starting from 1870 British subjects who naturalized as US citizens lost their British nationality. During this time, diplomatic incidents had also arisen between the US and several other European countries over their tendency to conscript naturalized US citizens visiting their former homelands. In addition, many 19th century European immigrants to the United States eventually returned to their homelands after naturalizing as US citizens and in some cases then attempted to use their US citizenship for diplomatic protection. The US State Department had to decide which US citizens it should protect and which were subjected to local law, resulting in tensions with immigrant communities in the US and European governments. In 1874, President Ulysses S. Grant, in his annual message to Congress, decried the phenomenon of people "claiming the benefit of citizenship, while living in a foreign country, contributing in no manner to the performance of the duties of a citizen of the United States, and without intention at any time to return and undertake those duties, to use the claims to citizenship of the United States simply as a shield from the performance of the obligations of a citizen elsewhere." The US government negotiated agreements with various European states known as the Bancroft Treaties from 1868 to 1937, under which the signatories pledged to treat the voluntary naturalization of a former citizen or national with another sovereign nation as a renunciation of their citizenship.
The theory of perpetual allegiance largely fell out of favor with governments during the late 19th century. With the consensus of the time being that dual citizenship would only lead to diplomatic problems, more governments began prohibiting it and revoking the nationality of citizens holding another nationality. By the mid-20th century, dual nationality was largely prohibited worldwide, although there were exceptions. For example, a series of United States Supreme Court rulings permitted Americans born with citizenship in another country to keep it without losing their US citizenship. Most nations revoked the nationality of their citizens who naturalized in another nation, as well as if they displayed significant evidence of political or social loyalty to another nation such as military service, holding political office, or even participating in elections. In some cases, naturalization was conditional on renunciation of previous citizenship. Many nations attempted to resolve the issue of dual citizenship emanating from people born in their territory but who inherited citizenship under the laws of another nation by requiring such individuals to choose one of their nationalities upon reaching the age of maturity. The US State Department, invoking provisions of the Bancroft treaties, systematically stripped US citizenship from naturalized US citizens who returned to live in their native countries for extended periods of time. However, in the absence of multilateral cooperation regarding dual nationality, enforcement was leaky. Many individuals continued to hold dual nationality by circumstance of birth, including most children born in the US to non-citizen parents.
At the League of Nations Codification Conference, 1930, an attempt was made to codify nationality rules into a universal worldwide treaty, the 1930 Hague Convention, whose chief aims would be to completely abolish both statelessness and dual citizenship. The 1930 Convention on Certain Questions Relating to the Conflict of Nationality Laws proposed laws that would have reduced both but, in the end, were ratified by only 20 nations. One significant development that emerged was the Master Nationality Rule, which provided that "a State may not afford diplomatic protection to one of its nationals against a state whose nationality such person also possesses."
Although fully eliminating dual nationality proved to be legally impossible during this time, it was subjected to fierce condemnation and social shaming. It was framed as disloyalty and widely compared to bigamy. George Bancroft, the American diplomat who would later go on to negotiate the first of the Bancroft treaties, which were named for him, stated in 1849 that nations should "as soon tolerate a man with two wives as a man with two countries; as soon bear with polygamy as that state of double allegiance." In 1915, former US President Theodore Roosevelt published an article deriding the concept of dual nationality as a "self-evident absurdity." Roosevelt's article was spurred by the case of P.A. Lelong, a US citizen born in New Orleans to French immigrant parents. He had planned to travel to France on business but had been warned that he might be conscripted to fight in World War I, and when he contacted the State Department for assurances that "my constitutional privileges as an American citizen follow me wherever I go", he was informed that France would regard him as a citizen under its jus sanguinis laws, and that the State Department could give no assurances regarding his liability for military service if he voluntarily placed himself in French jurisdiction.
However, the consensus against dual nationality began to erode as a result of changes in social mores and attitudes. By the late 20th century, it was becoming gradually accepted again. Many states were lifting restrictions on dual citizenship. For example, the British Nationality Act 1948 removed restrictions on dual citizenship in the UK, the 1967 Afroyim v. Rusk ruling by the US Supreme Court prohibited the US government from stripping citizenship from Americans who had dual citizenship without their consent, and the Canadian Citizenship Act, 1976, removed restrictions on dual citizenship in Canada. The number of states allowing multiple citizenships further increased after a treaty in Europe requiring signatories to limit dual citizenship lapsed in the 1990s, and countries with high emigration rates began permitting it to maintain links with their respective diasporas.
Each country sets its own criteria for citizenship and the rights of citizenship, which change from time to time, often becoming more restrictive. For example, until 1982, a person born in the UK was automatically a British citizen; this was subjected to restrictions from 1983. These laws may create situations where a person may satisfy the citizenship requirements of more than one country simultaneously. This would, in the absence of laws of one country or the other, allow the person to hold multiple citizenships. National laws may include criteria as to the circumstances, if any, in which a person may concurrently hold another citizenship. A country may withdraw its own citizenship if a person acquires a citizenship of another country, for example:
Once a country bestows citizenship, it may or may not consider a voluntary renunciation of that citizenship to be valid. In the case of naturalization, some countries require applicants for naturalization to renounce their former citizenship. For example, the US Chief Justice John Rutledge ruled "a man may, at the same time, enjoy the rights of citizenship under two governments", but the US requires applicants for naturalization to swear to an oath renouncing all prior "allegiance and fidelity" to any other nation or sovereignty as part of the naturalization ceremony. However, some countries do not recognise one of its citizens renouncing their citizenship. Effectively, the person in question may still possess both citizenships, notwithstanding the technical fact that they may have explicitly renounced one of the country's citizenships before officials of the other. For example, the UK recognizes a renunciation of citizenship only if it is done with competent UK authorities. Consequently, British citizens naturalized in the US remain British citizens in the eyes of the UK government even after they renounce British allegiance to the satisfaction of US authorities.
Irish nationality law applies to the whole of the island of Ireland, which at present is divided politically between the sovereign Republic of Ireland, which has jurisdiction over the majority of Ireland, and Northern Ireland, which consists of 6 of the 9 counties of the Irish province of Ulster, and is part of the United Kingdom. People in Northern Ireland are therefore "entitled to Irish, British, or both" citizenships.
Between 1999 and 24 June 2004, anyone born on the island of Ireland was entitled to Irish citizenship automatically. Since 24 June 2004 Irish citizenship has been granted to anyone born on the island of Ireland who has one, or both, parents who; are Irish citizens or British citizens, were entitled to live in Ireland without any residency restrictions, or was legally resident on the island of Ireland for 3 out of the 4 years immediately before their birth (excluding residence on a student visa, awaiting an international protection decision or residence under a declaration of subsidiary protection).
Some countries may take measures to avoid creation of multiple citizenship. Since a country has control only over who has its citizenship but has no control over who has any other country's citizenship, the only way for a country to avoid multiple citizenship is to deny its citizenship to people in cases when they would have another citizenship. This may take the following forms:
Countries may bestow citizenship automatically (i.e., "by operation of law"), which may result in multiple citizenships, in the following situations:
Some countries have special rules relating to multiple citizenships, such as:
Many countries allow foreigners or former citizens to live and work. However, for voting, being voted and working for the public sector or the national security in a country, citizenship of the country concerned is almost always required.
A statement that a country "does not recognize" multiple citizenship is confusing and ambiguous. Often, it is simply a restatement of the Master Nationality Rule, whereby a country treats a person who is a citizen of both that country and another in the same way as one who is a citizen only of the country. In other words, the country "does not recognize" that the person has any other citizenship for the purposes of the country's laws. In particular, citizens of a country may not be permitted to use another country's passport or travel documents to enter or leave the country, or be entitled to consulate assistance from the other country. Also, the dual national may be subject to compulsory military service in countries where they are considered to be nationals.
The concept of a "dormant citizenship" means that a person has the citizenships of two countries, but as long as while living permanently in one country, their status and citizen's rights in the other country are "inactive". They will be "reactivated" when they move back to live permanently in the other country. This means, in spite of dual citizenship, only one citizenship can be exercised at a time.
The "dormant citizenship" exists, for example, in Spain: Spanish citizens who have naturalized in an Iberoamerican country and have kept their Spanish citizenship are dual citizens, but have lost many of the rights of Spanish citizens resident in Spain—and hence the EU—until they move back to Spain. Some countries offer former citizens or citizens of former colonies of the country a simplified (re-)naturalization process. Depending on the laws of the two countries in question, dual citizenship may or may not be allowed. For details, see "right of return".
Another example of "dormant citizenship" (or "hidden citizenship") occurs when a person is automatically born a citizen of another country without officially being recognized. In many cases, the person may even be unaware that he holds multiple citizenship. For example, because of the nationality law in Italy, a person born in Canada to parents of Italian ancestry may be born with both Canadian and Italian citizenship at birth. Canadian citizenship is automatically acquired by birth within Canada. However, that same person may also acquire Italian citizenship at birth if at least one parent's lineage traces back to an Italian citizen. The person, their parent, grandparent, great-grandparent, and great-great-grandparent may have all transmitted the Italian citizenship to the next child in the line without even knowing it. Therefore, even if the person in this case may have been four generations removed from the last Italian-born (and therefore recognized) citizen, the great-great-grandparent, he would still be born with Italian citizenship. Even though the person may not even be aware of the citizenship, it does not change the fact that he is a citizen since birth. Therefore, the second citizenship (in this case, the Italian citizenship) is "dormant" (or "hidden") because the person does not even know he is a citizen and/or does not have official recognition from the country's government. That person would therefore have to gather all necessary documents and present them to the Italian government so that their "dormant" or "hidden" citizenship will be recognized. Once it is recognized, he will be able to do all of the things that any citizen could do, such as apply for a passport.
Some countries are more open to multiple citizenship than others, as it may help citizens travel and conduct business overseas. Countries that have taken active steps towards permitting multiple citizenship in recent years include Switzerland (since January 1, 1992) and Australia (since April 4, 2002).
It is often observed that dual citizenship may strengthen ties between migrants and their countries of origin and increase their propensity to remit funds to their communities of origin.
Qualitative research on the effect of dual citizenship on the remittances, diaspora investments, return migration, naturalization and political behavior finds several ways in which multiple citizenship can affect these categories. As a bundle of rights, dual citizenship (a) enables dual citizens by granting special privileges, (b) affects their expectations about privileges in the decision-making process, and (c) eases the transaction process and reduces costs and risks, for example in the case of investing and conducting business. In addition, a dual legal status can have positive effects on diasporic identification and commitment to causes in the homeland, as well as to a higher naturalization rate of immigrants in their countries of residence.
Multiple citizenship with non-resident citizen voting can result in dual transnational voting in contrast to the principle of one man, one vote.
A study published in 2007 in The Journal of Politics explored questions of whether allowing dual citizenship impedes cultural assimilation or social integration, increases disconnection from the political process, and degrades national or civic identity/cohesiveness.
The rise in tension between mainstream and migrant communities is cited as evidence of the need to maintain a strong national identity and culture. They assert that the fact that a second citizenship can be obtained without giving anything up (such as the loss of public benefits, welfare, healthcare, retirement funds, and job opportunities in the country of origin in exchange for citizenship in a new country) both trivializes what it means to be a citizen and nullifies the consequential, transformational, and psychological change that occurs in an individual when they go through the naturalization process.
In effect, this approach argues that the self-centered taking of an additional citizenship contradicts what it means to be a citizen, in that it becomes a convenient and painless means of attaining improved economic opportunity without any real consequences and can just as easily be discarded when it is no longer beneficial. Proponents argue that dual citizenship can actually encourage political activity providing an avenue for immigrants who are unwilling to forsake their country of origin either out of loyalty or based on a feeling of separation from the mainstream society because of language, culture, religion, or ethnicity.
A 2007 academic study concluded that dual citizens had a negative effect on the assimilation and political connectedness of first-generation Latino immigrants to the United States, finding dual citizens:
The study also noted that although dual nationality is likely to disconnect immigrants from the American political system and impede assimilation, the initial signs suggest that these effects seem to be limited almost exclusively to the first generation (although it is mentioned that a full assessment of dual nationality beyond the first generation is not possible with present data).
Concern over the effect of multiple citizenship on national cohesiveness is generally more acute in the United States. The reason for this is twofold:
The degree of angst over the effects of dual citizenship seemingly corresponds to a country's model for managing immigration and ethnic diversity:
People with multiple citizenship may be viewed as having dual loyalty, having the potential to act contrary to a government's interests, and this may lead to difficulties in acquiring government employment where security clearance may be required.
In the United States, dual citizenship is associated with two categories of security concerns: foreign influence and foreign preference. Contrary to common misconceptions, dual citizenship in itself is not the major problem in obtaining or retaining security clearance in the United States. As a matter of fact, if a security clearance applicant's dual citizenship is "based solely on parents' citizenship or birth in a foreign country", that can be a mitigating condition. However, taking advantage of the entitlements of a non-US citizenship can cause problems. For example, possession or use of a foreign passport is a condition disqualifying one from security clearance and "is not mitigated by reasons of personal convenience, safety, requirements of foreign law, or the identity of the foreign country" as is explicitly clarified in a Department of Defense policy memorandum which defines a guideline requiring that "any clearance be denied or revoked unless the applicant surrenders the foreign passport or obtains official permission for its use from the appropriate agency of the United States Government".
This guideline has been followed in administrative rulings by the United States Department of Defense (DoD) Defense Office of Hearings and Appeals (DOHA) office of Industrial Security Clearance Review (ISCR), which decides cases involving security clearances for Contractor personnel doing classified work for all DoD components. In one such case, an administrative judge ruled that it is not clearly consistent with US national interest to grant a request for a security clearance to an applicant who was a dual national of the U.S. and Ireland, despite the fact that it has with good relations with the US. In Israel, certain military units, including most recently the Israeli Navy's submarine fleet, as well as posts requiring high security clearances, require candidates to renounce any other citizenship before joining, though the number of units making such demands has declined. In many combat units, candidates are required to declare but not renounce any foreign citizenship.
On the other hand, Israel may view some dual citizens as desirable candidates for its security services because of their ability to legitimately enter neighbouring states which are closed to Israeli passport holders. The related case of Ben Zygier has caused debate about dual citizenship in Australia.
This perception of dual loyalty can apply even when the job in question does not require security clearance. In the United States, dual citizenship is common among politicians or government employees. For example, Arnold Schwarzenegger retained his Austrian citizenship during his service as a Governor of California while US Senator Ted Cruz renounced his Canadian citizenship birthright on 14 May 2014.
In 1999, the US Attorney General's office issued an official opinion that a statutory provision that required the Justice Department not to employ a non-"citizen of the United States" did not bar it from employing dual citizens.
In Germany, politicians can have dual citizenship. David McAllister, who holds British and German citizenship, was minister president of the State of Lower-Saxony from July 1, 2010, to February 19, 2013. He was the first German minister president to hold dual citizenship.
A small controversy arose in 2005 when Michaëlle Jean was appointed the Governor General of Canada (official representative of the Queen). Although Jean no longer holds citizenship in her native Haiti, her marriage to French-born filmmaker Jean-Daniel Lafond allowed her to obtain French citizenship several years before her appointment. Article 23-8 of the French civil code allows the French government to withdraw French nationality from French citizens holding government or military positions in other countries and Jean's appointment made her both de facto head of state and commander-in-chief of the Canadian forces. The French embassy released a statement that this law would not be enforced because the Governor General is essentially a ceremonial figurehead. Nevertheless, Jean renounced her French citizenship two days before taking up office to end the controversy about it.
However, former Canadian Prime Minister John Turner was born in the United Kingdom and still retained his dual citizenship. Stéphane Dion, former head of the Liberal Party of Canada and the previous leader of the official opposition, holds dual citizenship with France as a result of his mother's nationality; Dion nonetheless indicated a willingness to renounce French citizenship if a significant number of Canadians viewed it negatively. Thomas Mulcair, former Leader of the New Democratic Party and former leader of the Official Opposition in the Canadian House of Commons also holds dual citizenship with France.
In Egypt, dual citizens cannot be elected to Parliament.
The Constitution of Australia, in Section 44(i), explicitly forbids people who hold allegiance to foreign powers from sitting in the parliament of Australia. This restriction on people with dual or multiple citizenship being members of parliament does not apply to the state parliaments, and the regulations vary by state. A court case (see Sue v Hill) determined that the UK is a foreign power for purposes of this section of the constitution, despite Australia holding a common nationality with it at the time that the Constitution was written, and that Senator-elect Heather Hill had not been duly elected to the national parliament because at the time of her election she was a subject or citizen of a foreign power. However, the High Court of Australia also ruled that dual citizenship on its own would not be enough to disqualify someone from validly sitting in Parliament. The individual circumstances of the non-Australian citizenship must be looked at although the person must make a reasonable effort to renounce his or her non-Australian citizenship. However, if that other citizenship cannot be reasonably revoked (for example, if it is impossible under the laws of the other country or impossible in practice because it requires an extremely difficult revocation process), then that person will not be disqualified from sitting in Parliament. In the 2017 Australian parliamentary eligibility crisis, the High Court disqualified Australia's Deputy Prime Minister and four senators because they held dual citizenship, despite being unaware of their citizenship status when elected.
In New Zealand, controversy arose in 2003 when Labour MP Harry Duynhoven applied to renew his citizenship of the Netherlands. Duynhoven, the New Zealand-born son of a Dutch-born father, had possessed dual citizenship from birth but had temporarily lost his Dutch citizenship as a result of a change in Dutch law in 1995 regarding non-residents. While New Zealand's Electoral Act allowed candidates with dual citizenship to be elected as MPs, Section 55 of the Act stated that an MP who applied for citizenship of a foreign power after taking office would forfeit his/her seat. This was regarded by many as a technicality, however; and Duynhoven, with his large electoral majority, was almost certain to re-enter Parliament in the event of a by-election. As such, the Labour Government retrospectively amended the Act, thus enabling Duynhoven to retain his seat. The amendment, nicknamed "Harry's Law", was passed by a majority of 61 votes to 56. The revised Act allows exceptions to Section 55 on the grounds of an MP's country/place of birth, descent, or renewing a foreign passport issued before the MP took office.
Both the former Estonian president Toomas Hendrik Ilves and the former Lithuanian president Valdas Adamkus had been naturalized US citizens prior to assuming their offices. Both have renounced their US citizenships: Ilves in 1993 and Adamkus in 1998. This was necessary because neither individual's new country permits retention of a former citizenship. Adamkus was a high-ranking official in the Environmental Protection Agency, a federal government department, during his time in the United States. Former Latvian president Vaira Vīķe-Freiberga relinquished Canadian citizenship upon taking office in 1999.
In some cases, multiple citizenship can create additional tax liability. Almost all countries that impose tax normally base tax liability on source or residency. A very small number of countries tax their non-resident citizens on foreign income; examples include the United States, Eritrea, and the Philippines
Under Spanish tax law, Spanish nationals and companies still have tax obligations with Spain if they move to a country that is in the list of tax havens and cannot justify a strong reason, besides tax evasion. They are required to be residents of that country for a minimum of 5 years; after which they are free from any tax obligations.
U.S. persons living outside the United States are still subject to tax on their worldwide income, although U.S. tax law provides measures to reduce or eliminate double taxation issues for some, namely exemption of earned income (up to an inflation-adjusted threshold which, as of 2023, is $120,000), exemption of basic foreign housing, as well as foreign tax credits. It has been reported that some US citizens have relinquished US citizenship in order to avoid possible taxes, the expense and complexity of compliance, or because they have been deemed unacceptable to financial institutions in the wake of FATCA.
A person with multiple citizenship may have a tax liability to his country of residence and also to one or more of his countries of citizenship; or worse, if unaware that one of his citizenships created a tax liability, that country may consider the person to be a tax evader. Many countries and territories have signed tax treaties or agreements for avoiding double taxation.
Still, there are cases in which a person with multiple citizenship will owe tax solely on the basis of holding one such citizenship. For example, consider a person who holds both Australian and United States citizenship, and lives and works in Australia. He would be subject to Australian taxation, because Australia taxes its residents, and he would be subject to U.S. taxation because he holds U.S. citizenship. In general, he would be allowed to subtract the Australian income tax he paid from the U.S. tax that would be due. In addition, the U.S. will allow some parts of foreign income to be exempt from taxation; for instance, in 2018 the foreign earned income exclusion allowed up to US$103,900 of foreign salaried income to be exempt from income tax (in 2020, this was increased to US$107,600). This exemption, plus the credit for foreign taxes paid mentioned above, often results in no U.S. taxes being owed, although a U.S. tax return would still have to be filed. In instances where the Australian tax was less than the U.S. tax, and where there was income that could not be exempted from U.S. tax, the U.S. would expect any tax due to be paid.
The United States Internal Revenue Service has excluded some regulations such as Alternative Minimum Tax (AMT) from tax treaties that protect double taxation. In its current format even if U.S. citizens are paying income taxes at a rate of 56%, far above the maximum U.S. marginal tax rate, the citizen can be subject to US taxes because the calculation of the AMT does not allow full deduction for taxes paid to a foreign country. Other regulations such as the post date of foreign mailed tax returns are not recognized and can result in penalties for late filing if they arrive at the IRS later than the filing date. However, the filing date for overseas citizens has a two-month automatic extension to June 15.
"If you are a U.S. citizen or resident alien residing overseas, or are in the military on duty outside the U.S., on the regular due date of your return, you are allowed an automatic 2-month extension to file your return and pay any amount due without requesting an extension. For a calendar year return, the automatic 2-month extension is to June 15. If you are unable to file your return by the automatic 2-month extension date, you can request an additional extension to October 15 by filing Form 4868 before the automatic 2-month extension date. However, any tax due payments made after June 15 will be subject to both interest charges and failure to pay penalties." (IRS, 2012)
Many countries, even those that permit multiple citizenship, do not explicitly recognise multiple citizenship under their laws: individuals are treated either as citizens of that country or not, and their citizenship with respect to other countries is considered to have no bearing. This can mean (in Iran, Mexico, many Arab countries, and former Soviet republics) that consular officials abroad may not have access to their citizens if they also hold local citizenship. Some countries provide access for consular officials as a matter of courtesy but do not accept any obligation to do so under international consular agreements. The right of countries to act in this fashion is protected via the Master Nationality Rule.
Multiple citizens who travel to a country of citizenship are often required to enter or leave the country on that country's passport. For example, a United States Department of State web page on dual nationality contains the information that most US citizens, including dual nationals, must use a US passport to enter and leave the United States. Under the terms of the South African Citizenship Act, it is an offence for someone aged at least 18 with South African citizenship and another citizenship to enter or depart the Republic of South Africa using the passport of another country. Individuals who possess multiple citizenships, may also be required, before leaving a country of citizenship, to fulfill requirements ordinarily required of its resident citizens, including compulsory military service or exit permits. An example of this occurs in Israel, which permits multiple citizenships whilst also requiring compulsory military service for its citizens.
In accordance with the European Travel Information and Authorisation System (ETIAS), the EU citizens who have multiple nationalities will be obliged to use the passport issued by an EU Member State for entering the Schengen area.
Military service for dual nationals can be an issue of concern. Several countries have entered into a Protocol relating to Military Obligations in Certain Cases of Double Nationality established at The Hague, 12 April 1930. The protocol states "A person possessing two or more nationalities who habitually resides in one of the countries whose nationality he possesses, and who is in fact most closely connected with that country, shall be exempt from all military obligations in the other country or countries. This exemption may involve the loss of the nationality of the other country or countries." The protocol has several provisions.
The right to healthcare in countries with a public health service is often discussed in relation to immigration but is a non-issue as far as nationality is concerned. The right to use public health services may be conditioned on nationality and/or on legal residency. For example, anyone legally resident and employed in the UK is entitled to use the National Health Service; non-resident British citizens visiting Britain do not have this right unless they are UK state pensioners who hold a UK S1 form.
The potential issues that dual nationality can pose in international affairs have long been recognized, and as a result, international law recognizes the concept of "dominant and effective nationality", under which a dual national will hold only one dominant and effective nationality for the purposes of international law to one nation that holds their primary national allegiance, while any other nationalities are subordinate. The theory of dominant and effective nationality emerged as early as 1834. Customary international law and precedent have since recognized the idea of dominant and effective nationality, with the Nottebohm case providing an important shift. The International Court of Justice defines effective nationality as a "legal bond having as its basis a social fact of attachment, a genuine connection of existence, interests and sentiments, together with the existence of reciprocal rights and duties". International tribunals have adopted and used the principle. Under customary international law, tribunals dealing with questions involving dual nationality must determine the effective nationality of the dual national by determining to which nation the individual has more of a "genuine link". Unlike dual nationality, one may only be the effective national of a single nation, and different factors are taken into consideration to determine effective nationality, including habitual residence, family ties, financial and economic ties, cultural integration, participation in public life, armed forces service, and evidence of sentiment of national allegiance.
Source: German Federal Government (as of July 2023)
Citizens of these countries may keep their old citizenship if naturalizing in a country that forbids dual citizenship or that country may refuse their naturalization.
Dual citizenship is allowed in Angola, Burundi, Comoros, Cabo Verde, Côte d'Ivoire, Djibouti, Gabon, Gambia, Ghana, Kenya, Malawi, Mali, Morocco, Mozambique, Niger, Nigeria, Rwanda, Senegal, São Tomé and Príncipe, Sierra Leone, Sudan, Tunisia, Uganda, Zambia and Zimbabwe; others restrict or forbid dual citizenship. Lesotho observes dual citizenship, as well as jus soli. There are problems regarding dual citizenship in Namibia. Eritreans, Egyptians, and South Africans wanting to take another citizenship need permission to maintain their citizenship, though multiple citizenship acquired from birth is not affected. Eritrea taxes its citizens worldwide, even if they have never lived in the country. Equatorial Guinea does not allow dual citizenship, but it is allowed for children born abroad, if at least one parent is a citizen of Equatorial Guinea. Tanzania and Cameroon do not allow dual citizenship.
Most countries in the Americas allow dual citizenship, some only for citizens by descent or with other countries, usually also in the region with which they have agreements. Some countries (e.g., Argentina, Bolivia) do not allow their citizens to renounce their citizenship, so their nationals retain it even when naturalizing in a country that forbids dual citizenship. Most countries in the region observe unconditional jus soli, i.e. a child born there is regarded as a citizen even if the parents are not. Some countries, such as the Dominican Republic, Ecuador, Guatemala, Honduras, Mexico, Nicaragua, and Uruguay, allow renunciation of citizenship only if it was involuntarily acquired by birth to non-citizen parents.
Dual citizenship is restricted or forbidden in Cuba, Suriname, Panama, and Guyana.
Most countries in Asia restrict or forbid dual citizenship. In some of these countries (e.g. Iran, North Korea, Kuwait), it is very difficult or even impossible for citizens to renounce their citizenship, even if a citizen is naturalized in another country.
EU and EFTA countries have varying policies regarding dual citizenship. Under EU rules, a citizen of one EU or EFTA country can live and work indefinitely in the other EU and EFTA countries. However, countries can limit the right to vote and work in certain sensitive fields (such as government, police, military) to local citizens only. Immigrants from another EU or EFTA country can be refused welfare benefits. Welfare fraud may result in deportation. Economically inactive EU citizens who want to stay longer than three months in another Member State have to fulfill the condition of having health insurance and "sufficient resources" in order not to become an "unreasonable burden" for the social assistance system of the host Member State, which otherwise can legitimately expel them. For consular protection in non-EU/non-EFTA countries, immigrants must contact the embassy of the country of their citizenship, not the one of their guest country (exception: In countries where there is no embassy of their home country, citizens of an EU country have the right to get consular protection from the embassy of any other EU country present in that country.)
Within the EU, mandatory military service exists, at least in peacetime, only in Austria, Cyprus, Estonia, Finland, and Greece (In all countries but Cyprus, alternative service is available). Within the EFTA countries, only Switzerland requires it (alternative service is available); Iceland and Liechtenstein have no armed forces; in Norway, military service is de jure mandatory, but the enforcement is limited, so some sources claim it is de facto voluntary.
For details, see the nationality law of the country concerned and Citizenship of the European Union.
The Nordic Passport Union allows citizens of Denmark (including the Faroe Islands), Sweden, Norway, Finland and Iceland to travel and reside in other Nordic countries without a passport or a residence permit.
Irish and British citizens enjoy freedom of movement in each other's country (Common Travel Area).