Nationality and Citizenship in International Law: Concept, Acquisition, and Loss

Nationality serves as the fundamental legal bond linking an individual to a sovereign state under international law, enabling access to global rights and state protection. While often used interchangeably with citizenship, nationality defines a person's international status, whereas citizenship governs domestic civil and political rights. This article provides a comprehensive overview of how nationality is acquired—ranging from birth (jus soli) and descent (jus sanguinis) to naturalization, registration, and territorial changes—and the legal mechanisms through which it can be lost.

Nationality serves as the fundamental link allowing individuals to access rights and protections guaranteed by international law. When a state exercises authority over its nationals—whether they are living in their homeland or traveling abroad—it does so under its personal sovereignty. International legal frameworks recognize this authority while establishing boundaries to prevent jurisdictional overreach.

Distinguishing Nationality from Citizenship

Although commonly used as synonyms, nationality and citizenship represent distinct legal concepts:

Nationality defines an individual's legal bond to a sovereign state on the global stage. It is recognized under international law and identifies a person's affiliation with a nation regardless of their internal political rights.
Citizenship pertains strictly to domestic or municipal law. It reflects a person's legal standing within a country, conferring full civil and political rights (such as voting or holding public office).

Because international law focuses on state sovereignty and international personality, the concept of citizenship remains largely internal to domestic legal systems. Consequently, while all citizens hold the nationality of their respective state, not all nationals necessarily possess full citizenship rights.

Example: Under the U.S. Nationality Act of 1940, residents of certain non-state U.S. territories owe allegiance to the United States and are recognized globally as U.S. nationals, yet they do not hold full U.S. citizenship rights within domestic law.

How Nationality Is Acquired

Every sovereign nation establishes its own criteria for granting nationality through domestic legislation. Consequently, methods of acquiring nationality vary globally, though they generally fall into eight recognized categories:

1. By Birth (Jus Soli)

The principle of jus soli grants nationality based on being born within a nation's territorial boundaries, a system widely used in countries like the United Kingdom, the United States, and several Latin American nations.

India's legal framework for birthright citizenship has shifted over time:

Indian Citizenship Act of 1955: Originally granted citizenship to anyone born in India after January 26, 1950, regardless of the parents' nationality.
1986 Amendment: Restricted birthright citizenship to individuals with at least one parent holding Indian citizenship at the time of birth (excluding children of foreign diplomats and enemy aliens).
2003 Amendment: Enacted stricter criteria. Children born after 2003 qualify only if both parents are Indian citizens, or if one parent is an Indian citizen and the other is not an illegal migrant. This progression marks India's transition from pure jus soli toward a descent-based system.

2. By Descent (Jus Sanguinis)

Under jus sanguinis, nationality is inherited through parental lineage rather than place of birth. Nations such as Germany and France rely primarily on this principle.

India incorporates descent-based rules under Section 4 of the Citizenship Act:

1992 Amendment: Permitted individuals born outside India to gain citizenship if either parent was an Indian citizen, provided the birth was registered at an Indian consulate within one year or one parent was in Indian government service.
2003 Amendment: Clarified that for births outside India between 1950 and 1992, the father had to be an Indian citizen. For births after December 10, 1992, either parent's citizenship suffices. Minors holding dual citizenship through descent must formally renounce their foreign citizenship within six months of turning 18.

3. By Naturalization

Naturalization is the process by which a person voluntarily acquires a new nationality later in life through application, marriage, adoption, prolonged residence, or government service. States possess full discretion to grant or deny naturalization requests and cannot force naturalization upon individuals against their will.

Under Section 6 of India's Citizenship Act, eligible non-citizens (excluding illegal migrants) can apply for naturalization by meeting specific Third Schedule requirements:

Originating from a country that does not prohibit Indian citizens from naturalizing.
Agreeing to renounce prior nationality upon approval.
Satisfying residency/service benchmarks (at least 12 consecutive months preceding the application, plus 11 out of the preceding 14 years).
Demonstrating good moral character and proficiency in an official language listed in the Eighth Schedule of the Indian Constitution.
Taking an oath of allegiance to India.

4. By Resumption (Reintegration)

Individuals who previously lost their nationality can regain it under specific conditions. Section 8(2) of the Indian Citizenship Act allows individuals who lost Indian citizenship during their childhood (due to their parents' renunciation) to resume citizenship by submitting an application within one year of attaining legal adulthood (age 18).

5. By Subjugation

When a state or territory is annexed or conquered by another sovereign power, the inhabitants automatically acquire the nationality of the acquiring state. For instance, following the annexation of Austria by Germany, Austrian citizens became German nationals.

Similarly, Section 7 of the Indian Citizenship Act stipulates that residents of newly incorporated territories automatically gain Indian citizenship on a date specified by executive order (e.g., the Goa, Daman, and Diu Citizenship Order of 1962).

6. By Cession

When a sovereign state cedes a portion of its land to another state through a treaty or agreement, the population residing in the ceded territory typically shifts nationality to the acquiring state.

7. By Option

When a nation undergoes partition, boundary realignments, or territorial exchanges, affected residents are often granted the legal right to choose (option) which successor state's nationality they wish to adopt.

8. By Registration

Many legal systems allow specific groups of non-citizens to gain nationality through formal administrative registration. Section 5 of the Indian Citizenship Act extends this pathway to:

Persons of Indian Origin (PIO) who have resided in India for at least seven years.
Persons married to Indian citizens who have lived in India for seven years.
Minor children of Indian citizens.
Individuals with at least one parent who was a citizen of independent India, after residing in India for one year prior to applying.

Overseas Citizens of India (OCI) cardholders registered for five years who have lived in India for two years before applying.

How Nationality Is Lost

Just as nationality can be obtained, it can also be terminated through various legal mechanisms:

Mode of Loss	Description	Key Legal Details / Indian Context
Release	A state permits a citizen to voluntarily surrender their nationality upon approval of a formal request.	Requires explicit state authorization.
Deprivation	Involuntary revocation of citizenship by the state due to specific misbehavior or disqualifying acts.	Applies to cases involving fraud during naturalization, disloyalty, illegal trading during war, or remaining abroad for 7 consecutive years without registration. Requires due process to prevent statelessness.
Renunciation	A voluntary declaration by a person holding multiple nationalities to surrender one of them.	Under Section 8 of the Indian Citizenship Act, an adult can declare renunciation (subject to restriction during wartime). Minor children lose citizenship concurrently but retain resumption rights upon turning 18.
Substitution	Automatic loss of original nationality upon acquiring citizenship in another nation.	Section 9(1) of the Indian Citizenship Act enforces strict automatic termination upon voluntary acquisition of foreign nationality to prevent dual citizenship.
Expiration	Loss of nationality resulting from prolonged residence abroad combined with a failure to maintain legal links.	Enforced by statutes in certain nations when citizens remain abroad past a statutory time limit without renewing ties.