Maastricht University runs a dataset tracking the nationality rules of 200 countries back to 1960, built by researchers reading the legislation of each country directly. Its finding on the direction of travel is stark: taking a foreign passport cost people their original citizenship in more than 60% of countries in 1960, and in only 26% of countries by 2019.
What a count of surviving bans cannot capture is how many of them actually function. In a good number of countries, the prohibition operates as a warning label rather than a working system. Nobody is checking, no penalty is attached, or the state lacks the legal power to act on what it finds.
That gap decides whether a second passport is a paperwork nuisance or the loss of everything a person was born with. It also fluctuates. Two countries eased the law over the past year, a supreme court erased one ban retroactively, and a Gulf state converted a dormant rule into the largest citizenship-stripping campaign in modern history.
Three Rules That Get Mistaken for One
Some countries do not ban a second nationality at all. They simply refuse to see it, treating a person as their citizen alone the moment he crosses the border.
Poland is the standard example of this confusion. Polish law does not say a citizen is forbidden from holding a second passport; it says Polish officials must ignore it and deal with him as a Pole only. Poland’s supreme administrative court has confirmed that the rule was never a prohibition, yet the country still turns up on published lists of places that forbid dual citizenship.
A second group genuinely prohibits it and acts on it. Others prohibit it on paper and do nothing. Those last two may look identical on paper but could not be more different in practice.
Where Nobody is Checking
🇯🇵 Japan is the most documented case anywhere. Japanese law says that anyone holding two nationalities must pick one, and that taking a foreign citizenship by choice costs a person the Japanese one automatically.
The enforcement design undercuts the rule completely. File the form declaring you have chosen Japan and the obligation is treated as met, with no further contact from the ministry. Should the other nationality then quietly survive, the law asks only that the person “strive to renounce” it.
Nobody follows up. An estimated 700,000 dual citizens over the age of 22 live in Japan, alongside an uncountable population abroad, and the government has never moved against any of them. Courts have repeatedly declined to disturb the arrangement.
🇹🇭 Thailand may be the cleaner example, and it draws far less attention. Thai law provides that a citizen who naturalizes abroad loses Thai nationality, which sounds decisive until anyone looks for an instance of it happening.
There isn’t one. No involuntary revocation on that ground has appeared in the government gazette since the law passed in 1965, and the settled reading is that the minister may act only when a person applies to leave voluntarily. The foreign ministry, meanwhile, supports dual nationals at its posts abroad and publishes guidance on using two passports correctly.
Thailand’s 2017 constitution then closed the door from the other side, forbidding revocation of citizenship from anyone born Thai. Six decades, no cases, and a constitutional bar protecting the largest affected group.
Where the Rule Enforces Itself
🇮🇳 India is the mirror image of Japan. The law is equally absolute, and unlike Japan, it works, because enforcement never depends on anyone being caught.
Loss is automatic on naturalizing abroad, and the Passports Act makes holding or travelling on an Indian passport afterwards an offence. What makes the rule bite is what comes next. Almost everyone who leaves wants the Overseas Citizen of India card, which restores visa-free travel, and consulates will not issue it, or an ordinary visa, without a surrender certificate proving the old passport has been cancelled. The former citizen walks into the consulate voluntarily and presents the evidence against himself.
“Once an Indian citizen acquires foreign citizenship, Indian citizenship ceases,” says Sachit Kumar, Managing Director of Globe Detective Agency. The loss itself rarely surprises anyone, he notes, but many clients “are not always aware of the practical renunciation and passport-surrender requirements” that follow. The most common mistake, in his experience, is continuing to use the Indian passport after taking another nationality; his advice is to complete the renunciation and surrender promptly to avoid breaching Indian law.
The penalties for that mistake are graded and modest: 10,000 rupees for each trip taken on the Indian passport after a three-month grace period, capped at 50,000, and 25,000 for each renewal. The point is that they are collected at the consulate, at the moment the person needs something from it. The result is a rule that produces a paper trail of a size no other country in this article can match. Just over 206,000 Indians formally renounced citizenship in 2024, and close to 900,000 did so between 2020 and 2024.
What replaces citizenship is the OCI card, which, as Kumar puts it, “does not give them the same rights as Indian citizenship.”
Where the Punishment is Optional
Egypt and Saudi Arabia share a structure that looks strict and behaves loosely. Both require citizens to obtain government permission before taking a foreign nationality, and neither makes the consequence automatic.
🇪🇬 Egyptian law is unusually blunt about the result. Take a foreign passport without permission and the person continues to be regarded as solely Egyptian in every respect, unless the cabinet separately decides to strip him. Breaking the rule produces nothing by default.
Practitioners see the same thing on the ground. “In my experience, I have never come across an Egyptian client whose citizenship was revoked for obtaining a second nationality,” says Mohamed Hassan of WorldGate Citizenship.
Even so, his firm advises Egyptian clients to “formally notify the Egyptian Passports Authority and the Ministry of Interior when acquiring a foreign nationality.”
🇸🇦 Saudi Arabia works the same way. Its law reserves the government’s right to revoke citizenship from someone who took a foreign nationality without approval, which is a discretionary power rather than automatic loss. Until the state chooses to use it, the person remains Saudi.
🇮🇷 Iran belongs in a footnote here rather than on the list. Its rules do bite, forcing property sales and imposing a permanent bar from ministerial, parliamentary, and council office, but they are applied selectively against people the state has already decided to target.
Where the Constitution Blocks the Law
Two countries keep a prohibition on the books that their own constitutions render unusable.
🇪🇪 Estonia requires that anyone holding Estonian and another nationality give one up within three years of turning 18. The constitution simultaneously forbids stripping citizenship from anyone who acquired it by birth.
The contradiction is open and unresolved. Estonia’s Chancellor of Justice raised it, the interior ministry insisted there was no problem, and the practical outcome is that Estonians by birth keep both nationalities for life while naturalized citizens cannot.
🇿🇼 Zimbabwe is the African twin. Its citizenship act still prohibits holding a foreign nationality without renouncing it, while the 2013 constitution protects citizens by birth.
The Constitutional Court settled which one wins. Ruling in the Mawere case, it held that dual citizenship is not prohibited for citizens by birth, a decision that restored citizenship for large numbers of Zimbabweans abroad. Cabinet approved principles for amending the act in 2019, with the attorney general acknowledging plainly that the act and the constitution were inconsistent.
Where Enforcement Barely Registers
🇰🇿 Kazakhstan bans dual citizenship in its constitution and polices it at a volume close to a rounding error. Border officers identified 1,190 cases in 2024, and the interior ministry penalized 675 people administratively that year, in a country of roughly 20 million.
The penalty is a fine of up to about $2,200 or expulsion, not a criminal charge. Kazakhstan’s own government portal states plainly that many citizens neglect the rules and use various methods to hold both nationalities at once.
In 2025, a member of parliament complained that identified suspects can still freely leave the country and announced he would push for criminal liability. Whether that goes anywhere is the thing to watch.
🇨🇳 China has banned dual citizenship for decades while struggling to spot it. Local police and overseas consulates did not share records, so people held a Chinese household registration and a foreign passport at the same time without anyone connecting the two.
That is now changing. New nationwide exit and entry rules take effect on 15 September 2026, widening the grounds on which citizens can be stopped at the border and blocked from leaving.
🇹🇿 Tanzania prohibits dual nationality for adults, with criminal language attached, and six citizens challenged those provisions in a constitutional case filed in 2022. Reporting from Dar es Salaam describes a diaspora that quietly holds both while fearing exposure.
Parliament has refused to soften the position. A proposed “Diaspora Tanzanite Card” would have granted former citizens entry, property, and inheritance rights short of nationality, valid for ten years and renewable. Lawmakers stripped it from the bill in September 2024, then did so again in January 2025.
🇪🇸 In Spain, naturalizing Spaniards from most countries outside the Ibero-American world must renounce their previous nationality at the oath ceremony, but that renunciation is spoken to a Spanish official and generally carries no legal weight in the country being renounced. Widespread dual nationality follows, which Spain neither formally recognizes nor pursues.
Kuwait is the Reason None of This is Forever
🇰🇼 In Kuwait, dual nationality was an open secret for decades. Then the state decided to act on a rule it had left dormant, and the campaign it launched in August 2024 has not stopped since.
Revocations passed 12,000 within three months, reaching around 50,000 by August 2025. An independent monitor tracking decrees in the official gazette counted more than 71,000 cases by mid-April 2026, equal to 4.6% of the citizen population. Counting spouses, children, and grandchildren who derived status through those individuals, one Kuwaiti academic puts the true reach at 250,000 to 300,000 people.
Holding a second nationality without authorization sits among the stated grounds. Kuwait’s interior ministry opened a hotline inviting the public to report dual nationals, with anonymity promised to informants.
The government then rewrote the underlying law by decree in April 2026, expanding ministerial powers and placing nationality decisions beyond judicial review. Any claim that a prohibition is “not really enforced” has to survive the Kuwaiti example first.
The Ban List is Shrinking
Three jurisdictions left this group over the past 15 months.
🇺🇦 Ukraine legalized multiple citizenship after decades of formal prohibition. President Zelensky signed the law in July 2025, it took effect on 16 January 2026, and it initially covers five approved countries: the United States, Canada, Germany, Poland, and the Czech Republic. Russian citizenship is excluded outright.
🇻🇳 Vietnam amended its nationality law with effect from 1 July 2025, widening the categories of people who may keep a foreign nationality when acquiring or restoring Vietnamese citizenship.
🇿🇦 South Africa produced the most instructive outcome of the three. Its Constitutional Court struck down the automatic loss rule on 6 May 2025 and ordered that everyone caught by it be treated as never having lost citizenship, reaching back to 1995.
The case was brought on behalf of South Africans who had lost their citizenship without knowing. A prohibition can be enforced sporadically enough that its own victims never learn it applies to them, then vanish entirely once someone finally litigates it.
🇱🇹 Lithuania shows the opposite pattern. A May 2024 referendum on allowing dual citizenship won a majority of the votes cast and failed anyway, because turnout fell short of the constitutional threshold.
How to Read a Prohibition
Treat an unenforced law as a description of the present rather than a permanent state. Kuwait’s rule did not change before the revocations began; the political decision to use it did.
The better question is what the state would have to do in order to act. In the Netherlands and Austria, loss happens by itself and surfaces at passport renewal, so the rule bites without anyone deciding anything. Egypt and Saudi Arabia need a minister to sign something, and until he does, nothing happens.
Constitutional protection for citizens by birth is the second thing worth checking, and the route to citizenship in any given country is worth confirming before assuming any of it. That single feature separates Estonia and Zimbabwe, where the prohibition cannot reach most people, from Indonesia and India, where it reaches everyone. Roughly 8,000 Indonesians formally renounced citizenship over five years, a number that, like India’s, only appears where a rule genuinely works.
Political salience is the third. Nepal’s prohibition sat unused against ordinary citizens for years, then removed a sitting deputy prime minister from office in 2023 once his American citizenship became a live question.
In practice, this means quiet jurisdictions aren’t necessarily safe; they may be quiet, but that could change in a single cabinet meeting.
