Multiple citizenship

• 1. Introduction

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  Multiple citizenship is the legal status of being recognized simultaneously as a national by more than one country. No international convention governs who holds which nationality. Each nation sets its own rules, and those rules frequently conflict with one another, which is precisely how multiple citizenship arises in the first place.

  For most of recorded history, holding more than one nationality was not a problem that needed solving. Migration was too rare and too slow for governments to care. But when people began moving in large numbers, the old assumptions cracked. Countries of origin refused to release their grip on emigrants who had naturalized elsewhere. The results were sometimes dramatic: men conscripted into armies they had tried to leave behind, sailors seized at sea, returning emigrants charged with treason. The War of 1812 was partly triggered by British naval impressment of US sailors whom Britain still claimed as its own subjects.

  The debate that followed has never really ended. By the mid-20th century, most governments had outlawed dual nationality outright. By the late 20th century, many had reversed course. Today, the questions circle the same anxieties they always have: what does citizenship actually mean, who controls it, and what happens when two countries disagree about the same person?

• 2. Perpetual Allegiance and Early Conflict

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  Until the late 19th century, many states traced their authority over citizens back to the feudal doctrine of perpetual allegiance, the idea that once a subject, always a subject, with no exit permitted without royal permission. When mass migration made that doctrine unworkable, the consequences spilled into international incidents.

  The aftermath of the 1867 Fenian Rising put the conflict in sharp relief. Irish-born men who had naturalized as American citizens traveled to Ireland to join the uprising. British authorities arrested them and charged them with treason, because in British eyes they had never stopped being British subjects. The outrage among Irish-Americans was intense. The UK's response, pointing out that US law also recognized perpetual allegiance, only sharpened the pressure on Congress to act.

  Congress responded with the Expatriation Act of 1868, which gave Americans the legal right to freely renounce their US citizenship. The UK followed within two years, providing that British subjects who naturalized as US citizens lost their British nationality from 1870 onward. The problem did not disappear there. Nineteenth-century European immigrants who had naturalized as Americans and then returned home sometimes tried to invoke US diplomatic protection, forcing the US State Department to decide which citizens it was actually obligated to defend. President Ulysses S. Grant, in his State of the Union address to Congress, decried people who claimed the benefit of citizenship while living abroad, contributing nothing to its duties, using American status purely as a shield against obligations elsewhere.

  The US government addressed the issue through a series of bilateral accords with European states known as the Bancroft Treaties, negotiated from 1868 through 1937. George Bancroft, the American diplomat the treaties were named for, had made the moral stakes plain as early as 1849, arguing that nations should as soon tolerate a man with two wives as a man with two countries.

• 3. The Push to Abolish It

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  By the early 20th century, the intellectual and political consensus against dual nationality was fierce. Theodore Roosevelt published an article in 1915 calling the concept a self-evident absurdity. His argument was sparked by a real case: P.A. Lelong, a US citizen born in New Orleans to French immigrant parents, wanted assurance from the State Department that his constitutional rights as an American would follow him to France. The State Department could give him none. France considered him a citizen under its jus sanguinis laws, and if he entered French jurisdiction voluntarily, he could be conscripted to fight in World War I.

  At the League of Nations Codification Conference in 1930, delegates tried to convert the consensus into binding international law. The 1930 Convention on Certain Questions Relating to the Conflict of Nationality Laws aimed at eliminating both statelessness and dual citizenship, but in the end only 20 nations ratified it. One lasting product of that conference was the Master Nationality Rule: a state may not offer diplomatic protection to one of its nationals against another state whose nationality that person also holds.

  Social shaming reinforced legal pressure. Dual nationality was widely compared to bigamy. Most nations revoked the nationality of citizens who naturalized elsewhere or who showed strong loyalty to a foreign state through military service, holding political office, or participating in elections. Many required people born with two nationalities to choose one upon reaching adulthood. Enforcement, however, was uneven. Children born in the US to non-citizen parents quietly accumulated dual nationalities generation after generation, and a series of US Supreme Court rulings eventually protected Americans born with foreign citizenship from losing their US status involuntarily.

• 4. The Gradual Reversal

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  The tide began turning in the late 20th century, driven by court decisions, legislative reforms, and the practical interests of countries with large diasporas. The British Nationality Act 1948 removed restrictions on dual citizenship in the UK. The 1967 US Supreme Court ruling in Afroyim v. Rusk prohibited the government from stripping citizenship from Americans who held dual nationality without their own consent. Canada's Citizenship Act of 1976 lifted its restrictions as well.

  A European treaty that had required signatories to limit dual citizenship lapsed in the 1990s, and more states in Europe began to permit it. Nations with high emigration rates found a practical reason to embrace multiple citizenship: allowing emigrants to keep their original nationality helped maintain cultural and economic ties with diaspora communities.

  Switzerland formally moved to allow multiple citizenship from the 1st of January 1992. Australia followed from the 4th of April 2002. Germany, which had restricted dual citizenship for decades, passed an act to modernize its Nationality Act effective the 27th of June 2024, allowing dual citizenship in all cases. German citizens no longer lose their citizenship by acquiring a foreign one, and foreigners naturalizing in Germany are no longer required to surrender ties to their home country. The law is not retroactive, however, and does not automatically restore citizenship to anyone who lost it under the previous rules.

• 5. How Citizenship Accumulates

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  Two foundational legal principles generate most instances of multiple citizenship: jus soli, citizenship by birth on a country's territory, and jus sanguinis, citizenship by descent through a parent or ancestor. When a country using one principle recognizes a child born under the other, the child can emerge from birth holding two passports before making any choice at all.

  A child born in the US to Austrian parents automatically holds both US and Austrian citizenship, even though Austria generally restricts dual nationality, because the US grants unconditional birthright citizenship. Italy's jus sanguinis law is particularly far-reaching: a person born in Canada to parents of Italian ancestry may hold both Canadian and Italian citizenship at birth, inheriting Italian nationality through an unbroken chain stretching back to a recognized Italian citizen great-great-grandparent. The person may be entirely unaware of the second citizenship. That is the concept of dormant or hidden citizenship: the status exists in law whether or not the holder knows about it or has had it formally recognized.

  Other routes include citizenship by marriage, which some countries grant immediately and others grant only after a waiting period. Iran is among the few that bestow citizenship on the wedding day itself. Algeria and some other states revoke the spouse's citizenship if the marriage ends within a specified period. Citizenship by investment exists in Antigua and Barbuda, Grenada, Dominica, Saint Kitts and Nevis, and Saint Lucia, as well as in Vanuatu, Montenegro, Turkey, and Jordan, with most programs conferring citizenship immediately upon passing due diligence, without any physical presence requirement. Vatican City operates on an entirely different basis: citizenship there is tied to holding an office, expires when the office ends, and cannot be inherited by children, which is why Vatican citizenship automatically carries an exception permitting dual status.

• 6. Rights, Obligations, and Restrictions

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  Holding citizenship in two countries confers benefits on both sides: the right to a passport, to enter and live in each country, to work, to own property, and to vote. The obligations travel with it too, including potential liability for national service and taxation on worldwide income.

  The US and Eritrea are among a very small number of countries that tax the worldwide income of their citizens regardless of where those citizens live. As of 2023, the US exemption for foreign earned income stands at $120,000. It has been reported that some US citizens have relinquished their citizenship specifically to escape the compliance costs and complexity that come with being taxable everywhere, a pressure made more acute by the reporting requirements of the Foreign Account Tax Compliance Act.

  Many countries that allow dual citizenship still refuse to recognize the second nationality within their own borders. A dual national may be barred from seeking consular help from the other country while on the territory of the first. Countries including Egypt and Armenia bar dual citizens from election to Parliament. Australia's constitution explicitly forbids anyone holding allegiance to a foreign power from sitting in federal Parliament. In the 2017-18 Australian parliamentary eligibility crisis, fifteen members of Parliament were found ineligible due to dual citizenship they had often not known they held. Israel requires diplomats and members of Parliament to renounce any other citizenship before taking office, though the number of military units demanding the same has declined. Colombia bars dual citizens from serving as ministers of foreign affairs or defense. New Zealand allows dual citizens to serve as MPs but prohibits them from voluntarily acquiring another citizenship once in office, with one notable exception: the passage of retroactive legislation nicknamed "Harry's Law" protected Labour MP Harry Duynhoven after he renewed his Dutch citizenship in 2003.

• 7. Dual Loyalty and Political Controversy

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  The suspicion that multiple citizenship implies divided loyalty has shaped both security policy and political careers. In the United States, holding a foreign passport is a disqualifying condition for security clearance and is not mitigated by personal convenience, safety, or even a requirement under foreign law. A Department of Defense policy memorandum states that clearance must be denied or revoked unless the applicant surrenders the foreign passport or obtains official government permission for its use.

  The issue surfaces at the highest levels of politics. Arnold Schwarzenegger retained his Austrian citizenship throughout his service as Governor of California. Ted Cruz renounced his Canadian birthright citizenship on the 14th of May 2014, while serving as a US senator. In Canada, a small controversy arose in 2005 when Michaelle Jean was appointed Governor General. Her marriage to French-born filmmaker Jean-Daniel Lafond had given her French citizenship, and Article 23-8 of the French civil code potentially permitted France to withdraw nationality from citizens who held government or military positions abroad. Although the French embassy stated the law would not be enforced, Jean renounced her French citizenship two days before taking office. Former Canadian Prime Minister John Turner, born in the United Kingdom, retained his dual citizenship throughout his public career without the same controversy.

  A 2007 study published in The Journal of Politics examined how dual citizenship affected first-generation Latino immigrants in the United States. Dual citizens in that study were 32 percent less likely to be fluent in English, 18 percent less likely to identify as American, 19 percent less likely to consider the US their homeland, and 15 percent less likely to have ever voted in a national election. The study noted, however, that these effects appeared to be largely limited to the first generation, and that a full assessment across subsequent generations was not possible with the data then available.

• 8. Quadruple Citizenship and Unusual Cases

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  Association football goalkeeper Nikita Haikin is cited as a prominent case of quadruple citizenship, illustrating that the concept of multiple nationality extends well beyond the dual variety most legal frameworks address. The number of countries allowing multiple citizenship has grown steadily, and the range of circumstances that can produce it has broadened alongside formal policy changes.

  The concept of effective nationality exists in international law to manage the complications that arise when multiple citizenships collide in international disputes. The International Court of Justice defines effective nationality as a legal bond resting on a social fact of attachment, a genuine connection of existence, interests, and sentiments, together with the existence of reciprocal rights and duties. International tribunals use factors including habitual residence, family ties, financial connections, cultural integration, participation in public life, and armed forces service to determine which nationality is dominant. The Nottebohm case provided an important shift in how this principle is applied. Unlike formal citizenship, which a person can hold in several countries at once, effective nationality is singular: a person can have only one, regardless of how many passports they carry.