Naturalization (or naturalisation) is the legal act or process by which a non-citizen in a country may acquire citizenship or nationality of that country. It may be done automatically by a statute, i.e., without any effort on the part of the individual, or it may involve an application or a motion and approval by legal authorities. The rules of naturalization vary from country to country but typically include a promise to obeying and upholding that country's laws, taking and subscribing to the oath of allegiance, and may specify other requirements such as a minimum legal residency and adequate knowledge of the national dominant language or culture. To counter multiple citizenship, most countries require that applicants for naturalization renounce any other citizenship that they currently hold, but whether this renunciation actually causes loss of original citizenship, as seen by the host country and by the original country, will depend on the laws of the countries involved.
The massive increase in population flux due to globalization and the sharp increase in the numbers of refugees following World War I created a large number of stateless persons, people who were not citizens of any state. In some rare cases, laws for mass naturalization were passed. As naturalization laws had been designed to cater for the relatively few people who had voluntarily moved from one country to another (expatriates), many western democracies were not ready to naturalize large numbers of people. This included the massive influx of stateless people which followed massive denationalizations and the expulsion of ethnic minorities from newly created nation states in the first part of the 20th century, but they also included the mostly aristocratic Russians who had escaped the 1917 October Revolution and the war communism period, and then the Spanish refugees. As Hannah Arendt pointed out, internment camps became the "only nation" of such stateless people, since they were often considered "undesirable" and were stuck in an illegal situation, wherein their country had expelled them or deprived them of their nationality, while they had not been naturalized, thus living in a judicial no man's land.
Since World War II, the increase in international migrations created a new category of migrants, most of them economic migrants. For economic, political, humanitarian and pragmatic reasons, many states passed laws allowing a person to acquire their citizenship after birth, such as by marriage to a national – jus matrimonii – or by having ancestors who are nationals of that country, in order to reduce the scope of this category. However, in some countries this system still maintains a large part of the immigrant population in an illegal status, albeit with some massive regularizations, for example, in Spain by José Luis Zapatero's government and in Italy by Berlusconi's government.
Laws by country
The People's Republic of China gives citizenship to persons with one or two parents with Chinese nationality who have not taken residence in other countries. The country also gives citizenship to people born on its territory to stateless people who have settled there. Furthermore, individuals may apply for nationality if they have a near relative with Chinese nationality, if they have settled in China, or if they present another legitimate reason. In practice, only few people gain Chinese citizenship; as of 2010, China had only 1,448 naturalised Chinese in total.
The naturalization process starts with a written application. Applicants must submit three copies, written with a ball-point or fountain pen, to national authorities, and to provincial authorities in the Ministry of Public Security and the Public Security Bureau. Applicants must also submit original copies of a foreign passport, a residence permit, a permanent residence permit, and four two-and-a-half inch long pictures. According to the conditions outlined in the Nationality Law of the People's Republic of China, authorities may also require "any other material that the authority believes are related to the nationality application".
People who fulfil all of the following criteria can obtain French citizenship through naturalisation:
At least 5 years' residence, although reduced to the following minimum periods in certain situations: 2 years: Successfully completed 2 years of studies with a view to obtaining a degree or diploma at a French higher educational institution; Made an exceptional contribution to France's standing and influence in the arts, science, sport, culture, academia, entrepreneurship, etc. No minimum residence period: Performed military service with the French Army; Served voluntarily in wartime in the French Army or an allied army; Rendered exceptional service to France (requires personal ministerial approval); Attained the official status of a refugee in France; Citizen of a member state of the Organisation internationale de la Francophonie and have French as their native language or have completed at least 5 years of schooling in a French-speaking educational establishment.
Integration into French society, including adhering to the values and principles of the Republic, and having a sufficient knowledge of French history, culture and society;
Sufficient spoken command of the French language;
No serious criminal convictions, defined as follows: Never been sentenced to more than 6 months' imprisonment (not including suspended sentences) for any crime (unless the applicant has been legally deemed rehabilitated or the sentence has been wiped from their criminal record); Never been convicted of any crime that counters France's fundamental interests (unless the applicant has been legally deemed rehabilitated or the sentence has been wiped from their criminal record); Never been convicted of any act of terrorism (unless the applicant has been legally deemed rehabilitated or the sentence has been wiped from their criminal record).
The fee for naturalisation is €55, except in French Guiana, where it is €27.50.
People who fulfil all of the following criteria can obtain German citizenship through naturalisation:
At least 8 years' residence in Germany with a valid residence permit. This minimum period is reduced for the following: 7 years for people who have successfully completed an official integration course; 3 years for spouses and registered same-sex partners of a German citizen (must have been married or in the registered partnership for at least 2 years at the time of application).
Declaring allegiance to the German Constitution;
Sufficient command of the German language;
No serious criminal convictions.
The dependent minor children of an applicant for naturalisation may also themselves become naturalised German citizens.
The fee for standard naturalisation is €255, while it is €51 per dependent minor child naturalised along with their parent. The fee may be waived in cases of extreme hardship or public interest.
Loss of previous citizenship
People who naturalise as German citizens must usually give up their previous nationality, as German law takes a restrictive approach to multiple citizenship. Exceptions are made for:
EU and Swiss citizens, provided that the law of their country of origin does not prohibit the acquisition of another citizenship;
Citizens of countries where renouncing one's citizenship is too difficult or humiliating (e.g. Afghanistan), prohibitively expensive (e.g. the United States) or legally impossible (e.g. Argentina).
The Indian citizenship and nationality law and the Constitution of India provides single citizenship for the entire country. The provisions relating to citizenship at the commencement of the Constitution are contained in Articles 5 to 11  in Part II of the Constitution of India. Relevant Indian legislation is the Citizenship Act 1955, which has been amended by the Citizenship (Amendment) Act 1986, the Citizenship (Amendment) Act 1992, the Citizenship (Amendment) Act 2003  , and the Citizenship (Amendment) Ordinance 2005  . The Citizenship (Amendment) Act 2003 received the assent of the President of India on 7 January 2004 and came into force on 3 December 2004. The Citizenship (Amendment) Ordinance 2005 was promulgated by the President of India and came into force on 28 June 2005.
Following these reforms, Indian nationality law largely follows the jus sanguinis (citizenship by right of blood) as opposed to the jus soli (citizenship by right of birth within the territory).
Automatically Jus sanguinis: for birth; If an Italian citizen recognizes, at a time after birth, a minor child; For adoption; To obtain or re-obtain from a parent.
Following declaration By descent; Jus soli: by birth or descent in Italy;
By marriage or naturalization By marriage: the foreign or stateless spouse of an Italian citizen may acquire Italian citizenship after two years of legal residence in Italy or, if residing abroad, after three years from the date of marriage; By naturalization: the foreigner can apply for Italian citizenship after ten years of legal residence in Italy, reduced to five years for those who have been recognized as stateless or refugee and four years for citizens of countries of the European Community.
Indonesian nationality is regulated by Law No. 12/2006 (UU No. 12 Tahun 2006). The Indonesian nationality law is based on jus sanguinis and jus soli. The Indonesian nationality law does not recognize dual citizenship except for persons under the age of 18 (single citizenship principle). After reaching 18 years of age individuals are forced to choose one citizenship (limited double citizenship principle).
A foreign citizen can apply to become an Indonesian citizen with the following requirements:
Age 18 or older, or married
Resided in Indonesia for a minimum of 5 consecutive years or 10 non-consecutive years
Physically and mentally healthy
Ability to speak Indonesian and acknowledge Pancasila and Undang-Undang Dasar Negara Republik Indonesia Tahun 1945
Never convicted of a crime for which the punishment is imprisonment for one year or more
If having Indonesian citizenship will not give the person dual citizenship
Employed or have fixed income
Pay citizenship fee
Any application for citizenship is granted by the President of Indonesia.
Israel's Declaration of Independence was made on 14 May 1948, the day before the British Mandate was due to expire as a result of the United Nations Partition Plan. The Israeli parliament created two laws regarding immigration, citizenship and naturalization: the Law of Return and the Israeli nationality law. The Law of Return, enacted on July 15, 1950, gives Jews living anywhere in the world the right to immigrate to Israel. This right to immigrate did not and still does not grant citizenship. In fact, for four years after Israel gained independence, there were no Israeli citizens.
On July 14, 1952, the Israeli parliament enacted the Israeli Nationality Law. The Nationality Law naturalized all citizens of Mandated Palestine, the inhabitants of Israel on July 15, 1952, and those who had legally resided in Israel between May 14, 1948, and July 14, 1952. The law further clarified that naturalization was available to immigrants who had arrived before Israel's creation, immigrants who arrived after statehood was granted, and those who did not come to Israel as immigrants but have since expressed desire to settle in Israel, with restriction. Naturalization applicants must also meet the following requirements: be over 18 years of age, have resided in Israel for three out of the five preceding years, have settled or intend to settle permanently in Israel, have some knowledge of Hebrew, and have renounced prior nationality or demonstrated ability to renounce nationality after becoming a citizen of Israel.
Because of Israel's relatively new and culturally mixed identity, Israel does not grant citizenship to persons born on Israeli soil. Instead, the government chose to enact a jus sanguinis system, with the naturalization restrictions listed above. There is currently no legislation on second-generation immigrants (those born in Israel to immigrant parents). Furthermore, foreign spouses can apply for citizenship through the Minister of the Interior, but have a variety of restrictions and are not guaranteed citizenship.
People who fulfil all of the following criteria can obtain Luxembourg citizenship through naturalisation:
At least 18 years old.
At least 5 years of legal residence in Luxembourg, including an uninterrupted period of one year immediately before applying for citizenship.
Passing a Luxembourgish language exam.
Taking a course on "Living together in the Grand Duchy" and passing the associated examination.
Never having been handed an immediate custodial sentence of 12 months or more or a suspended custodial sentence of 24 months or more, in any country.
Naturalisation in Malaysia is guided by the 1964 Malaysian Constitution. According to the law, those who want to be the country citizen should live in the country for a period of 10–12 years. The would-be-citizens are required to speak the Malay language as well submitting the identity cards of two Malaysians who recommend the applicant for citizenship. As the Government of Malaysia does not recognise dual citizenship, those who seek naturalisation are needed to reside permanently in the country and renouncing their former country citizenship.
The applicant shall appear before the Registrar of Citizenship when submitting the application.
The applicant must be aged 21 years and above on the date of the application.
The applicant has resided in the federation for a period of not less than 10 years in a period of 12 years, including the 12 months immediately preceding the date of application.
The applicant intends to reside permanently in the federation.
The applicant is of good character.
The applicant has adequate knowledge of the Malay language.
The applicant must be sponsored by two referees who are citizens aged 21 years and above and who are not relatives, not hired persons, and not advocates or solicitors to the applicant.
Form C must be completed and submitted together with copies of the necessary documents.
Commonwealth Act No. 473, the Revised Naturalization Law, approved June 17, 1939, provided that persons having certain specified qualifications may become a citizen of the Philippines by naturalization. Republic Act No. 9139, approved June 8, 2001, provided that aliens under the age of 18 who were born in the Philippines, who have resided in the Philippines and have resided therein since birth, and who possess other specified qualifications may be granted Philippines citizenship by administrative proceeding subject to certain requirements.
Naturalization in Russia is guided by articles 13 and 14 of the federal law “About Citizenship of Russian Federation” passed on May 31, 2002. Citizenship of Russia can be obtained in general or simplified order. To become a citizen in general order, one must be 18 years of age or older, continuously live in Russia as a permanent resident for at least five years (this term is limited to one year for valued specialists, political asylum seekers and refugees), have legal means of existence, promise to obey the laws and Constitution of Russia and be fluent in the Russian language.
There is also a possibility to naturalize in a simplified order, in which certain requirements will be waived. Eligible for that are persons, at least one parent of whom is a Russian citizen living on Russian territory; persons, who lived on the territories of the former Soviet republics but never obtained citizenships of those nations after they gained independence; persons, who were born on the territory of RSFSR and formerly held Soviet citizenship; persons married to Russian citizens for at least 3 years; persons, who served in Russian Armed Forces under contract for at least 3 years; parents of mentally incapacitated children over 18 who are Russian citizens; participants of the State Program for Assisting Compatriots Residing Abroad; and some other categories.
Chapter 2 of the South African Citizenship Act, enacted on October 6, 1995, defines who is considered a naturalized citizen at the time of the act and also outlines the naturalization process for future immigrants.
Any person who immediately prior to the commencement of the act had been a South African citizen via naturalization, had been deemed to be a South African citizen by registration, or had been a citizen via naturalization of any of the former states now composing South Africa is now considered to be a naturalized citizen of South Africa.
Those wishing to apply for naturalization in the future must apply to the Minister of Home Affairs and must meet a slew of requirements. First, naturalization applicants must be over the age of 18 and must have been a permanent resident of South Africa for one year prior to application and for four out of the eight years prior to application. Applicants must also demonstrate good character and knowledge of the basic responsibilities and privileges of a South African citizen. The ability to communicate in one of the official languages of South Africa is also required. Applicants must show the intention to reside in South Africa after naturalization, and they are required to make a declaration of allegiance. According to Article 3  , subsection 3 of the South African constitution, national legislation must provide for the acquisition, loss and restoration of citizenship.
Being a naturalized South African citizen is a privilege, not a right. Even after meeting all the requirements and going through the naturalization process, the minister holds the right to deny citizenship. Foreign spouses of South African citizens can apply for naturalization after two years of marriage, but is subject to potential denial of the minister. The minister can also grant citizenship to minors, if their parent applies for them.
The minister also holds the power to revoke naturalization at any time for specific reasons listed in the Act. Reasons for revoking the naturalization certificate include marrying someone who is a citizen of another country and holding citizenship in another country, or applying for citizenship of another country without prior authorization for retention of citizenship. If a permanent resident is denied naturalization, he or she must wait at least one year before reapplying.
There has always been a distinction in the law of England and Wales between the subjects of the monarch and aliens: the monarch's subjects owed the monarch allegiance, and included those born in his or her dominions (natural-born subjects) and those who later gave him or her their allegiance (naturalised subjects). Today, the requirements for naturalisation as a citizen of the United Kingdom depend on whether or not one is the spouse or civil partner of a citizen. An applicant who is a spouse or civil partner of a British citizen must:
hold indefinite leave to remain in the UK (or an equivalent such as Right of Abode or Irish citizenship)
have lived legally in the UK for three years
been outside of the UK no more than 90 days during the one-year period prior to filing the application.
show sufficient knowledge of life in the UK, either by passing the Life in the United Kingdom test or by attending combined English language and citizenship classes. Proof of this must be supplied with one's application for naturalisation. Those aged 65 or over may be able to claim exemption.
For those not married to or in a civil partnership with a British citizen, the requirements are:
Five years legal residence in the UK
Indefinite leave to remain or "equivalent" for this purpose (see above) must have been held for 12 months
the applicant must intend to continue to live in the UK or work overseas for the UK government or a British corporation or association
the same "good character" standards apply as for those married to British citizens
the same language and knowledge of life in the UK standards apply as for those married to British citizens.
"The sole authority to naturalize persons as citizens of the United States is conferred upon the Attorney General." In particular cases, however, federal judges may enjoin the Attorney General to confer U.S. nationality upon a person. The term "Attorney General" in the Immigration and Nationality Act (INA) includes any immigration judge or member of the Board of Immigration Appeals (BIA).
The INA states the following:
No person, except as otherwise provided in this subchapter, shall be naturalized unless such applicant, (1) immediately preceding the date of filing his application for naturalization has resided continuously, after being lawfully admitted for permanent residence, within the United States for at least five years and during the five years immediately preceding the date of filing his application has been physically present therein for periods totaling at least half of that time, and who has resided within the State or within the district of the Service in the United States in which the applicant filed the application for at least three months, (2) has resided continuously within the United States from the date of the application up to the time of admission to citizenship, and (3) during all the periods referred to in this subsection has been and still is a person of good moral character, attached to the principles of the Constitution of the United States, and well disposed to the good order and happiness of the United States.
The Naturalization Act of 1795 set the initial rules on naturalization: "free, White persons" who had been resident for five years or more. An 1862 law allowed honorably discharged Army veterans of any war to petition for naturalization after only one year of residence in the United States. An 1894 law extended the same privilege to honorably discharged five-year veterans of the Navy or Marine Corps. Laws enacted in 1919, 1926, 1940, and 1952 continued preferential treatment provisions for veterans.
Following the Spanish–American War in 1898, Philippine citizens were classified as U.S. nationals, and the 1917 Jones–Shafroth Act granted U.S. citizenship to natives of Puerto Rico. But the 1934 Tydings–McDuffie Act reclassified Filipinos as aliens, and set a quota of 50 immigrants per year, and otherwise applying the Immigration Act of 1924 to them.
The Magnuson Act repealed the Chinese Exclusion Act. During the 1940s, 100 annual immigrants from British India and the Philippines were allowed. The War Brides Act of 1945 permitted soldiers to bring back their foreign wives and established precedent in naturalization through marriage. The Immigration Act of 1965 finally allowed people from all nations to be given equal access to immigration and naturalization.
Illegal immigration became a major issue in the United States at the end of the 20th century. The Immigration Reform and Control Act of 1986, while tightening border controls, also provided the opportunity of naturalization for illegal aliens who had been in the country for at least four years. Today, lawful permanent residents of the United States are eligible to apply for U.S. citizenship after five years, unless they continue to be married to a U.S. citizen, in which case they can apply after only three years of permanent residency.
The Child Citizenship Act of 2000 streamlined the naturalization process for children adopted internationally. A child under age 18 who is adopted by at least one U.S. citizen parent, and is in the custody of the citizen parent(s), is now automatically naturalized once admitted to the United States as an immigrant or when legally adopted in the United States, depending on the visa under which the child was admitted to the United States. The Act also provides that the non-citizen minor child of a newly naturalized U.S. citizen, whether by birth or adoption, also automatically receives U.S. citizenship
The following list is a brief summary of the duration of legal residence before a national of a foreign state, without any cultural, historical, or marriage ties or connections to the state in question, can request citizenship under that state's naturalization laws.
|Country||Residence requirement||Dual citizenship||Notes||Main article||Ref|
|Albania||5 years||Yes||Continuous residence||Albanian nationality law|||
|Andorra||20 years||No||Continuous residence as a permanent resident, unless the applicant has spent all of their mandatory education in Andorra in which case 10 years continuous as a permanent residence||Andorran nationality law|||
|Angola||10 years||Yes||Continuous residence||Angolan nationality law|||
|Argentina||2 years||Yes||Continuous residence||Argentine nationality law|||
|Armenia||3 years||Yes||Armenian nationality law|
|Australia||4 years||Yes||Legal residency in Australia, including one year as a permanent resident immediately prior to making an application||Australian nationality law|||
|Austria||10–30 years||No||Exceptions for those born in Austria, citizens of another EEA country, refugees or "exceptionally integrated" in which case it is 6 years.||Austrian nationality law|||
|Azerbaijan||5 years||No||The applicant must be a fluent speaker of the Azerbaijani language.||Azerbaijani nationality law|
|Belgium||5 years||Yes||Continuous residence||Belgian nationality law|||
|Bangladesh||5 years||Yes||Bangladeshi nationality law|||
|Barbados||5 years||Barbadian nationality law|||
|Belarus||7 years||Yes||Belarusian nationality law|||
|Benin||10 years||Yes||Beninese nationality law|
|Belize||5 years||Yes||Belizean nationality law|
|Bhutan||20 years||No||Bhutanese nationality law|||
|Bosnia and Herzegovina||8 years||Continuous residence||Bosnian nationality law|||
|Brazil||4 years||Yes||Uninterrupted residence.||Brazilian nationality law|||
|Bulgaria||5 years||Partial||Reduced to 3 years if the applicant is married to a Bulgarian national, was born in Bulgaria, or settled in the country before the age of 18. Citizens of the EU, EEA or Switzerland, as well as spouses of Bulgarian nationals, are not required to renounce their existing citizenship.||Bulgarian nationality law|||
|Burkina Faso||10 years||Burkinabé nationality law|||
|Cambodia||5 years||Yes||Cambodian nationality law|
|Canada||3 years||Yes||Three out of five years as a permanent resident.||Canadian nationality law|||
|Chile||5 years||Yes||Continuous residence||Chilean nationality law|
|Colombia||5 years||Yes||As a permanent resident||Colombian nationality law|
|Costa Rica||5–7 years||Yes||Requires proven knowledge of Spanish language and Costa Rica's history, having a way of living, no criminal records and two witnesses.||Costa Rican nationality law|||
|Croatia||8 years||Partial||Continuous residence; applicant must be a fluent Croatian speaker||Croatian nationality law|||
|Cuba||Yes||Foreigners can become naturalized citizens of Cuba since 2019.||Cuban nationality law|
|Cyprus||7 years||Yes||or by using the "Naturalization of Investors in Cyprus by Exception", a government run cash-for-passport program.||Cypriot nationality law|||
|Czech Republic||5 years||Yes||5 years as permanent residence or 10 years residence.||Czech nationality law|||
|Denmark||9 years||Yes||Continuous residence||Danish nationality law|||
|Egypt||10 years||Partial||Egyptian nationality law|
|El Salvador||1–5 years||Yes||Salvadoran nationality law|
|Estonia||8 years||No||Eight years residence out of which five years as a permanent residence.||Estonian nationality law|||
|Finland||5 years||Yes||Continuous residence||Finnish nationality law|
|Fiji||5 years||Five years of lawful residence out of the previous 10 years||Fijian nationality law|
|France||5 years||Yes||Continuous residency. Two years continuous residency for applicants who have had at least two years of higher education leading to a Master's degree or higher in France. No minimum residency requirement for applicants who have served in the French Army, rendered exceptional service to France, and some other cases.||French nationality law|
|Germany||8 years||Partial||Continuous residence. 7 years for applicants who have successfully completed an official integration course; 3 years for applicants who are married to, or in a registered same-sex partnership with, a German citizen||German nationality law|
|Greece||7 years||Yes||Greek nationality law|||
|Hungary||8 years||Yes||Continuous residence||Hungarian nationality law|||
|Iceland||7 years||Yes||Icelandic nationality law|||
|Iran||5 years||Yes||Become 18 years old and 5 years legal residence in Iran.||Iranian nationality law|
|Ireland||5 years||Yes||Irish nationality law|||
|Israel||5 years||Partial||To naturalize, three years out of the previous five years of residence is required and must have the right to reside in Israel on a permanent basis. However, Jews around the world may obtain Israeli citizenship upon arrival by the Law of Return.||Israeli citizenship law|
|Italy||10 years||Yes||The residence has to be continuous. The law provide some cases in which there is a faster access to naturalization: three years if at least one grandparent was/is Italian, four years for EU nationals, five years for refugees or stateless people.||Italian nationality law|
|Japan||5 years||No||Continuous residence; three years if married to a Japanese national.||Japanese nationality law|
|Jordan||15 years||Yes||Jordanian nationality law|
|Kazakhstan||5 years||No||Kazakhstani nationality law|
|Latvia||10 years||Yes, under certain conditions||Latvian nationality law|
|Lebanon||Yes||Foreigners cannot obtain Lebanese citizenship||Lebanese nationality law|
|Liberia||2 years||No||Liberian law allows members of other races to hold permanent residency status||Liberian nationality law|||
|Liechtenstein||10 years||Years spent in Liechtenstein under the age 20 count double||Liechtenstein nationality law|||
|Lithuania||10 years||No||Continuous residence as a permanent resident; seven years if married to a Lithuanian national.||Lithuanian nationality law|||
|Luxembourg||5 years||Yes||Twelve months' continuous residence prior to applying for naturalization; three years' residence if married to a Luxembourgish citizen. The applicant must pass the Luxembourgish language examinations or have had at least 7 years of education in a Luxembourgish school.||Luxembourgish nationality law|||
|Malawi||7 years||Five years for a person who is of an African race or has Commonwealth or Malawian ties||Malawian nationality law|
|Malta||5 years||Or a government run cash-for-passport program.||Maltese nationality law|||
|Mexico||5 years||Yes||Mexican nationality law|
|Moldova||10 years||Yes||Eight years for stateless citizens or recognised refugees||Moldovan nationality law|
|Monaco||10 years||No||Continuous residence||Monégasque nationality law|||
|Montenegro||10 year||No||Montenegrin nationality law||s|
|Mozambique||5 years||Yes||Mozambican nationality law|
|Myanmar||N/A||No||Foreigners cannot become naturalized citizens of Myanmar||Myanmar nationality law|||
|Netherlands||5 years||Partial||Continuous residence||Dutch nationality law|||
|New Zealand||5 years||Yes||Continuous residence||New Zealand nationality law|||
|North Macedonia||8 years||No||Continuous residence||Macedonian nationality law|||
|Norway||7 years||Yes||Seven years out of the previous 10 (with out-of-realm vacations of up to two months per year) as a permanent resident immediately before the application||Norwegian nationality law|||
|Oman||20 years||No||Omani nationality law|
|Paraguay||3 years||Paraguayan nationality law|||
|Peru||2 years||Yes||Continuous residence||Peruvian nationality law|
|Philippines||5–10 years||Yes||Continuous residence||Philippine nationality law|||
|Poland||10 years||Yes||Ten years residence or three years permanent residence||Polish nationality law|
|Portugal||5 years||Yes||Continuous residence||Portuguese nationality law|||
|Romania||8 years||Yes||Romanian nationality law|||
|San Marino||30 years||Fifteen years for foreigners married to a citizen of San Marino||Sammarinese nationality law|
|Russia||5 years||Yes||Continuous residence. Three years if married to a Russian citizen. One year for valued specialists and refugees.||Russian nationality law|||
|Samoa||5 years||Samoan nationality law|||
|Serbia||3 years||Yes||Continuous residence||Serbian nationality law|||
|Slovakia||8 years||Partial||Slovak nationality law|
|Slovenia||10 years||Yes||Ten years residence; five years continuous before the application.||Slovenian nationality law|||
|Spain||10 years||Partial||Two to five years||Spanish nationality law|||
|Somalia||7 years||No||Somalian nationality law|
|South Korea||5 years||Partial||Three years continuous if married to a South Korean national||South Korean nationality law|||
|Sweden||5 years||Yes||Four years continuous for stateless people and refugees||Swedish nationality law|||
|Switzerland||10 years||Yes||The years between the age of eight and eighteen count double, while a minimum of six years' residence is required||Swiss nationality law|||
|Taiwan||5 years||Partial||Nationality law of the Republic of China|
|Thailand||5 years||No||Continuous residence; applicant must have knowledge of the Thai language. Residence and language requirememts are waived for spouses and children of Thai citizens.||Thai nationality law|||
|Togo||5 years||No||Togolese nationality law|
|Tonga||5 years||Tongan nationality law|
|Turkey||5 years||Yes||Continuous residence; applicant must be a fluent speaker of the Turkish language.||Turkish nationality law|||
|Tunisia||5 years||Yes||Continuous residence; applicant must be a fluent speaker of the Arabic language.||Tunisia nationality law|
|Ukraine||5 years||Yes||Ukrainian nationality law|
|United Arab Emirates||30 years||No||Emirati nationality law|
|United Kingdom||5 years||Yes||Non-EU/EEA/Swiss citizens must have indefinite leave to remain before applying for naturalisation.||British nationality law|
|United States||5 years||Yes||Must have been physically present in the US for at least 30 of the 60 months preceding the application; ineligible if absent for a continuous period of 6 months or more during these 60 months.||United States nationality law|
|Uruguay||5 years||Yes||Three years if the applicant has a Uruguayan family member.||Uruguayan nationality law|
|Uzbekistan||5 years||No||Uzbekistani nationality law|
|Venezuela||10 years||Yes||Natural-born citizens of Spain, Portugal, Italy, Latin American or Caribbean country and have been legally living in Venezuela for 5 continuous years.||Venezuelan nationality law|
A few rare mass naturalization processes have been implemented by nation states. In 1891, Brazil granted naturalization to all aliens living in the country. In 1922, Greece massively naturalized all the Greek refugees coming from Turkey. The second massive naturalization process was in favor of Armenian refugees coming from Turkey, who went to Syria, Lebanon or other former Ottoman countries. Reciprocally, Turkey massively naturalized the refugees of Turkish descent or other ethnic backgrounds in Muslim creed from these countries during a redemption process.
Canada instituted a mass naturalization by Act of Parliament with the enactment of the Canadian Citizenship Act 1946.
After annexation of the territories east of the Curzon line by the Soviet Union in 1945, Soviets naturalized en masse all the inhabitants of those territories—including ethnic Poles, as well as its other citizens who had been deported into the Soviet Union, mainly to Kazakhstan. Those persons were forcibly naturalized as Soviet citizens. Later on, Germany granted to the ethnic German population in Russia and Kazakhstan full citizenship rights. Poland has a limited repatriation program in place.
The most recent massive naturalization case resulted from the Argentine economic crisis in the beginning of the 21st century. Existing or slightly updated right of return laws in Spain and Italy allowed many of their diasporic descendants to obtain—in many cases to regain—naturalization in virtue of jus sanguinis, as in the Greek case. Hence, many Argentines acquired European nationality.
Since the Fourteenth Amendment to the United States Constitution grants citizenship only to those "born or naturalized in the United States, and subject to the jurisdiction thereof", and the original United States Constitution only grants Congress the power of naturalization, it could be argued that all acts of Congress that expand the right of citizenship are cases of mass naturalization. This includes the acts that extended U.S. citizenship to citizens of Puerto Rico, the United States Virgin Islands, Guam, and the Northern Mariana Islands, as well as the Indian Citizenship Act of 1924 which made all Native Americans citizens (most of them were previously excluded under the "jurisdiction" clause of the 14th Amendment).
In the eastern Malaysian state of Sabah, mass naturalisation also happened during the administration of United Sabah National Organisation (USNO) and Sabah People's United Front (BERJAYA's) Muslim-dominated political parties to increase the Muslim population in the territory by naturalising immigrants and refugees from the mainly-Muslim dominated areas of Mindanao and Sulu Archipelago of the Philippines and Sulawesi of Indonesia.
In occupied territories
The mass naturalization of native persons in occupied territories is illegal under the laws of war (Hague and Geneva Conventions). However, there have been many instances of such illegal mass naturalizations in the 20th century.
Denaturalization is the reverse of naturalization, when a state deprives one of its citizens of his or her citizenship. From the point of view of the individual, denaturalization means revocation or loss of citizenship. Denaturalization can be based on various legal justifications. The most severe form is the "stripping of citizenship" when denaturalization takes place as a penalty for actions considered criminal by the state, often only indirectly related to nationality, for instance for having served in a foreign military. In countries that enforce single citizenship, voluntary naturalization in another country will lead to an automatic loss of the original citizenship; the language of the law often refers to such cases as "giving up one's citizenship" or (implicit) renunciation of citizenship. In another case, affecting only foreign-born citizens, denaturalization can refer to the loss of citizenship by an annulment of naturalization, also known as "administrative denaturalization" where the original act of naturalization is found to be invalid, for instance due to an administrative error or if it had been based on fraud (including bribery). In the US, the Bancroft Treaties in the 19th century regulated legislation concerning denaturalization.
In 2010, the U.S. government launched a program (Operation Janus) “to prevent aliens who received a final removal order under a different identity from obtaining immigration benefits”. In January 2018, for the first time, a denaturalization was performed as a result of this program, and a further program (Operation Second Look) was initiated by the HSI specifically to address leads received from Operation Janus. In June 2018, UCSIS announced an increase of the efforts to detect fraudulent naturalization cases, aiming at the revocation of the citizenship of individuals who had applied under false pretense.
Before World War I
In the United States, the proposed, but never ratified, Titles of Nobility amendment of 1810 would revoke the American citizenship of anyone who would "accept, claim, receive or retain, any title of nobility" or who would receive any gifts or honors from a foreign power.
Between World Wars
Before World War I, only a small number of countries had laws governing denaturalization that could be enforced against citizens guilty of "lacking patriotism". Such denaturalized citizens became stateless persons. During and after the war, most European countries passed amendments to revoke naturalization.
In Homo Sacer: Sovereign Power or Bare Life (1998), philosopher Giorgio Agamben mentioned a number of denaturalization laws that were passed after World War I by most European countries:
It is important to note that starting with the period of World War I, many European states began to introduce laws which permitted their own citizens to be denaturalized and denationalized. The first was France, in 1915, with regard to naturalized citizens of "enemy" origins; in 1922 the example was followed by Belgium, which revoked the naturalization of citizens who had committed "anti-national" acts during the war; in 1926 the Fascist regime in Italy passed a similar law concerning citizens who had shown themselves to be "unworthy of Italian citizenship"; in 1933 it was Austria's turn, and so forth, until in 1935 the Nuremberg Laws divided German citizens into full citizens and citizens without political rights. These laws—and the mass statelessness that ensued—mark a decisive turning point in the life of the modern nation-state and its definitive emancipation from the naive notions of "people" and "citizen"
The 1915 French denaturalization law applied only to naturalized citizens with "enemy origins" who had kept their original nationality. Later under Raymond Poincaré's government, another law was passed in 1927 which entitled the government to denaturalize any new citizen who committed acts contrary to the national interest.
In 1916, Portugal passed a law which automatically denaturalized all citizens born to a German father.
In 1922, Belgium enacted a law revoking the naturalization of persons accused of having committed "antinational acts" during the war; this was supplemented in 1934 by a new decree against people "in dereliction of their duties as Belgian citizens."
After 1926 in Italy, people who were deemed not to deserve the Italian citizenship or who were considered to represent a threat to the public order could lose their naturalization.
Egypt in 1926 and Turkey in 1928 enacted laws authorizing denaturalization of any person threatening the public order. Austria passed a similar law in 1933 by which it could denaturalize any citizen who participated in a hostile action against the state. Russia also passed several similar decrees after 1921.
In 1933, Nazi Germany passed a law authorizing it to denaturalize any person "living abroad" and began restricting the citizenship rights of naturalized citizens of Jewish origin, followed in 1935 by citizens by birth on the basis of the Nuremberg laws.
After World War II
In the United States
Yaser Esam Hamdi was a U.S. citizen captured in Afghanistan in 2001. He was fighting against U.S. and Afghan Northern Alliance forces, siding with the Taliban. He was named by the Bush administration as an illegal enemy combatant, and militarily detained in the country for almost three years without receiving any charges. On September 23, 2004, the U.S. Justice Department agreed to release Hamdi to Saudi Arabia on the condition that he give up his U.S. citizenship, though since it was done under duress it is possible that he can later reclaim it.
In the United Kingdom
Section 4 of the British Nationality, Immigration and Asylum Act 2002 gave power to the Home Secretary to ‘deprive a person of a citizenship status if the Secretary of State is satisfied that the person has done anything seriously prejudicial to the vital interests’ of the United Kingdom etc., except in the case where such might render the person stateless.
Under Canadian citizenship law citizenship can be revoked by an order from the federal cabinet if:
Naturalized Canadians is convicted of fraud in relation to their citizenship application or original admission to Canada as an immigrant
In the past (pre-1977) revoking citizenship was more broad:
Naturalization in another country
Long residence overseas (before 1967)
Loss based on parent's loss of Canadian citizenship
Those who are revoked can appeal to the Federal Court of Canada.
In South Africa
In Apartheid-era South Africa, the Bantu Homelands Citizenship Act, 1970, removed South African citizenship from Black South Africans, making them citizens of nominally-independent or self-governing tribal "homelands", the Bantustans — none of which achieved international recognition. In parallel with the creation of the homelands, South Africa's black population was subjected to a massive programme of forced relocation. It has been estimated that 3.5 million people were forced from their homes from the 1960s through the 1980s, many being resettled in the Bantustans.
With the demise of the apartheid regime in South Africa in 1994, the Bantustans were dismantled and their territory reincorporated into the Republic of South Africa. The drive to achieve this was spearheaded by the African National Congress as a central element of its programme of reform. The Bantu Homelands Citizenship Act itself was repealed by the 1993 Interim Constitution, with all citizens being restored to their South African citizenship.
History of citizenship
European Convention on Nationality
Convention on the Reduction of Statelessness