The historical evolution of political systems has led to the development of two models of citizenship acquisition: jus sanguinis (right of blood) and jus soli (right of soil). In certain situations, the convergence of these principles may necessitate the application of conflict-of-law rules.

An interesting example is provided by a judgment of the Supreme Administrative Court (ref. no. II OSK 1048/23), issued in 2025 but based on a Polish Act of 1920; it concerned the determination of the citizenship of a person of Polish descent whose ancestors were born in Brazil.

Acquiring Polish citizenship – rights and obligations of citizens of the Republic of Poland

In legal and political terminology, the term ‘citizenship’ refers to the bond linking a natural person to a state. Acquiring the citizenship of a given state entails the acquisition of rights and obligations established by its legal system (voting rights, full participation in economic activity, defence duties and tax liabilities). The historical circumstances in which individual states operated influenced their political systems, which could not fail to have an impact on the provisions adopted in those states regarding the acquisition of citizenship.

Ius sanguinis: acquisition of Polish citizenship by virtue of the right of blood

In the course of this evolution, two general models of citizenship acquisition took shape. The first of these is ius sanguinis (literally ‘the law of blood’): citizenship of a given state is acquired by virtue of being born to parents who are its citizens. This model was adopted by those countries in which a strong sense of national identity (based on blood ties) remained a defining feature, and where sustained immigration from abroad was not only a marginal phenomenon but also one that was frowned upon by their administrative bodies and public opinion. On the other hand, it was common for entire families of citizens to emigrate abroad for economic or political reasons. This model was adopted in Polish law (we have written more about the ways of acquiring Polish citizenship here: https://lexplorers.pl/en/how-to-obtain-polish-citizenship/).

Ius soli in Brazil: Brazilian citizenship according to the principle of jus soli

The second of the models mentioned is expressed by the principle of ius soli (‘right of the soil’ or even – more literally  – ‘right of the earth’). It operates in countries whose citizenry has been shaped by mass migration (countries of the Western Hemisphere). Citizenship under the ius soli model is acquired by virtue of being born on the territory of a given state. The legislation of individual countries introduces certain exceptions to this rule, mainly for the children of persons with no connection to the country of residence (e.g. diplomats).

Neither model currently exists in its pure form – most modern states apply hybrid solutions. This does not, however, alter the fact that one of them – ius sanguinis or ius soli – retains its fundamental character within them. In a situation where the citizenship rights of states, each of which has adopted a different model of citizenship acquisition, overlap, conflicts between the solutions applied in them may lead to disputes between individuals and public authorities.

Citizenship status under the Brazilian Constitution

Brazil serves as an example of a country that has adopted the ius soli model. The tradition of applying the principle whereby Brazilian citizenship is acquired on the basis of ius soli dates back at least to the Constitution of the United States of Brazil (as the country was then known) of 1891. Article 69 of that Constitution provided:

The citizens of Brazil are:

1) persons born in Brazil, even if their father is a foreign national, unless the father is residing in Brazil in the service of his country;

2) children of a Brazilian father and the illegitimate children of a Brazilian mother, born in a foreign country, provided they take up permanent residence in the Republic;

3) children of a Brazilian father who is stationed in another country in the service of the Republic, even if they do not reside there;

4) foreigners who,,  whilst residing in Brazil on 15 November 1889do not declare within six months of the Constitution coming into force their intention to retain their original nationality;

5) foreigners who own property in Brazil and are married to Brazilians or have Brazilian children, provided that they reside in Brazil, unless they express their intention not to change their nationality;

6) foreigners who have otherwise acquired citizenship.

The acquisition of citizenship under the principle of ius soli is also provided for in the current Constitution of the Federative Republic of Brazil of 1988. Among the main changes compared to previous constitutions is the removal of discrimination against women and children born out of wedlock:

Article 12

The following are Brazilians:

I – by birth:

a) those born in the Federative Republic of Brazil, even if their parents are foreigners, provided that the latter are not in the service of their own country;

b) those born abroad to a Brazilian father or a Brazilian mother, provided that one of them is in the service of the Federative Republic of Brazil;

c) born abroad to a Brazilian father or a Brazilian mother, provided that they reside in the Federative Republic of Brazil and opt at any time for Brazilian citizenship;

II – by naturalisation:

a) those who have acquired Brazilian citizenship in accordance with the provisions of the law; persons from Portuguese-speaking countries are required only to have resided in Brazil for one year without interruption and to be of good character;

b) foreigners, regardless of their nationality, who have resided in the Federative Republic of Brazil continuously for more than fifteen years and have not been convicted by a court, provided they apply for Brazilian citizenship.

Can a Brazilian citizen obtain Polish citizenship? The conflict between Brazilian ius soli and Polish ius sanguinis

As we have indicated, the existence of grounds for acquiring citizenship under the principles of ius soli and ius sanguinis may lead to a conflict. This occurs and in particular in situations where the law of a given state explicitly excludes the possibility of simultaneously holding the citizenship of another state. It is worth noting the obvious: the acquisition of citizenship as a result of an event such as being born to specific parents on the territory of a particular state, although it occurs without any action on the part of the individual, permanently shapes their legal status.

An interesting example of a dispute arising from the conflict between the principles of ius soli and ius sanguinis is provided by a recent judgment of the Supreme Administrative Court of 4 November 2025, ref. no. II OSK 1048/23. A Brazilian citizen approached the Mazovian Province Governor; due to her Polish roots, she was interested in obtaining confirmation that she held Polish citizenship.

Acquiring foreign citizenship on the basis of jus soli does not deprive one of Polish citizenship

The applicant’s great-grandfather (born in 1910) was a Polish citizen who emigrated to Brazil – where her grandmother was also born. Under the ius soli principle in force in Brazil, the applicant’s grandmother acquired Brazilian citizenship. In the opinion of the authority – shared by the provincial administrative court – pursuant to Article 11(1) of the Act of 20 January 1920 on Citizenship of the Polish State (Journal of Laws U. No. 7, item 44, as amended ), the applicant’s grandmother lost her Polish citizenship upon reaching the age of majority. The Polish Act in force between 1920 – and 1951 excluded the possibility of a Polish citizen holding the citizenship of another state (Article 1).

The Supreme Administrative Court aptly summarised this situation. The reasoning states: In this case, a specific circumstance arose which was not expressly provided for by the regulations, namely that the acquisition of two citizenships took place simultaneously, at a single moment, i.e. at the person’s birth, irrespective of any actions taken by them. There was a concurrence of two citizenships, based on two different principles – ius sanguinis (right of blood) and ius soli (right of soil). At the same time, the provisions do not specify the sequence of acquiring these citizenships, in particular, to give priority to either of them or to assign precedence.

Elaborating on this point, the Supreme Administrative Court did not accept the reasoning of the court of first instance and upheld the appeal. In its view, aforementioned   provided for theActan exception to the rule prohibiting dual citizenship for persons subject to universal military service. The legislature therefore sought a provision that would exclude the acquisition of another citizenship after obtaining Polish citizenship. Such an interpretation – as the Supreme Administrative Court rightly emphasised – is also supported by  Article 6(1) of the Regulation of the Minister of Internal Affairs of 7 June 1920 on the implementation of the Act of 20 January 1920 on Polish citizenship, pursuant to which Polish citizenship was lost by anyone who, of their own volition, acquired the citizenship of another state. In the case of the complainant’s grandmother, it is difficult to speak of her own volition, since the acquisition of Brazilian citizenship occurred as a result of her birth in that country. Thus, the complainant’s father, on the basis of ius sanguinis, also acquired Polish citizenship (as the son of a Polish citizen).

Ius soli as the basis for acquiring Argentine citizenship without losing Polish citizenship

It should be added that the Supreme Administrative Court (NSA) also applied a similar line of interpretation in a case involving a conflict between Polish and Argentine law, the latter also based on the ius soli model (judgment of the NSA of 19 December 2022, ref. no. II OSK 2095/21). Here, too, the court held that, under the 1920 Act on Polish Citizenship, one cannot speak of a “loss of Polish citizenship with deferred effect until reaching the age of majority” in the case of persons who acquired the citizenship of another state at birth on the basis of ius soli.

It is worth seeking out one’s Polish roots: a Brazilian of Polish descent

The emigration of Poles to the Americas – and thus to countries where the principle of ius soli applies – was a widespread phenomenon in the 20th century. It is therefore no coincidence that many people of Polish descent live there, who may be interested in confirming their Polish citizenship. Although public authorities are inclined (perhaps due to the risk of abuse of the practice of confirming Polish citizenship by people with Polish ancestors, but who are alien to Polish culture, in order to facilitate economic migration to the EU) to question Polish citizenship on the grounds of its alleged expiry upon the person reaching the age of majority, the case law of the administrative courts limits such an interpretation. This encourages those interested in obtaining or confirming Polish citizenship to search for Polish ancestors, even if the principle of ius soli applies in their current jurisdiction.

Support from GWW Law Firm in obtaining Polish citizenship

The lawyers at GWW provide comprehensive support to individuals who wish to apply for or confirm their Polish citizenship: https://gww.pl/en/specjalizacje/nationality-and-residence/. Although obtaining citizenship entails not only rights (such as participation in political life, purchasing property, and access to the EU labour market), but also obligations (e.g. in the area of national defence; for more on this: https://lexplorers.pl/polish-passport-rights-and-obligations-arising-from-citizenship/), it is worth taking advantage of one of the routes to acquiring Polish citizenship (we describe them on our blog:https://lexplorers.pl/en/how-to-obtain-polish-citizenship/).

The scope of services provided by GWW is not limited to support in procedures for acquiring Polish citizenship. If you would like to find out about our other areas of specialisation, please visit our website: gww.pl.