Mariam Sobayo was on the verge of feeling a sense of belonging to Ireland.
She was born in Dublin on February 10, 2005, just weeks after the country ended its long-standing practice of automatic citizenship for those born on Irish soil. Her parents immigrated to Ireland from Nigeria in 2001 and she is the youngest of five children. Her two older sisters were born in Ireland in 2002 and 2004 respectively.
Due to the difference in birth time, they automatically gained Irish citizenship. Sobayo spent years submitting documents and waiting for answers before finally receiving citizenship at the age of 18.
"I was born in Dublin, I never left Dublin," she said of growing up in the Irish capital, noting that she excelled in her school's Irish language course. “It’s like, ‘Oh, now there’s this new citizenship.’ And I want to say, I’ve been here since day one.”
Without her passport, she was unable to travel abroad, even when her classmates went on school trips. When her application for Irish citizenship was approved, she felt a mixture of relief and anger. "I feel like I'm carrying a heavy burden that shouldn't be mine," Sobayo said. She now works as a social worker looking after children seeking international protection.
In the coming weeks, the U.S. Supreme Court will rule on a landmark case in which the White House seeks to end the 157-year-old legal standard for birthright citizenship.
When President Trump talks about this issue, he calls the United States "stupid" for automatically granting citizenship to the children of immigrants born in the United States. The policy's laxity is indeed there for all to see: While many countries in Central and South America have similar laws, most require at least one parent to be a citizen for a child to be eligible for citizenship.
But research shows that stricter policies may undermine the potential of children who are born and raised in a country without citizenship, while easing them could improve prospects for the generation that benefits.
For example, a study last year by an international team of researchers found that compared with second-generation immigrants from other developed countries, the children of U.S. immigrants outperform their citizen children of the same age. Across the 12 countries studied, birthright citizenship was associated with higher economic mobility for children of immigrants.
“Of all the advanced economies in the world, the United States has been the most successful at integrating immigrants, and you might wonder why,” said Catalina Almuedo-Dorantes, an economics professor at the University of California, Merced. “Maybe it’s important to be able to get citizenship from very early on.”
"Parental Sins"
Distinguishing the effects of immigration policies in different countries is difficult because there are so many variables and there are few natural experiments that allow researchers to compare one group of people to another. Ireland's shift away from birthright citizenship provides one such experiment.
For most of Ireland's history, anyone born there was entitled to citizenship. The Good Friday Agreement that brought peace to Northern Ireland in 1998 was written into the Irish Constitution. This changed in 2005, when 79% of voters supported a referendum to remove birthright citizenship from the constitution.
The referendum came at a time of economic prosperity and improved quality of life in Ireland, transforming the country from a sending country of immigrants to a destination country for centuries. Ireland also faced some pressure from the then-young EU because it was the only member state to offer birthright citizenship, the right for all EU citizens to live and work anywhere in the EU.
But public debate has largely focused on claims that so-called "birth tourism" is causing overcrowding in maternity hospitals. In fact, the majority of non-Irish mothers giving birth in Ireland are European nationals with existing residency rights, and the pressure on hospitals stems mainly from insufficient funding. One study found that immigrants who arrived in Ireland between 1999 and 2004 were more educated and had fewer children than immigrants before and since.
Following the referendum, the citizenship of people born in Ireland on or after January 1, 2005, will depend on the nationality and residence history of their parents.
Samantha Arnold, senior manager at immigration consultancy Fragomen, explained that while the constitution no longer protects automatic birthright citizenship, other liberal provisions have been introduced.
Children born in Ireland who have at least one parent who was lawfully resident in the island for three of the four years before their birth can still obtain citizenship. Children born in Ireland who are not entitled to citizenship of another country are also eligible to prevent them becoming stateless.
"There are a lot of measures to try to catch people, but of course there are still people who will fall through the cracks," Arnold said. She added that those most likely to be denied citizenship are children whose parents do not have legal residence permits.
Eben Joseph, Special Rapporteur on Ireland's National Anti-Racism Action Plan, recently produced a documentary about young people born in Ireland shortly after the referendum to non-Irish parents who are still in limbo.
"It creates a huge policy gap that particularly affects the education and mental health of young people," Joseph said. "The sins of the parents are retributive on the children. If the parents are criminals or do not obtain citizenship for whatever reason, then the children have no way of obtaining citizenship."
More citizenship, more integration
The change in Ireland is so recent that little data has yet been produced to compare young adults born after 2005 with their slightly older peers. But there is more research on a similar change in Germany (in the opposite direction).
On January 1, 2000, Germany began granting citizenship to children at birth if at least one parent had been legally resident in Germany for eight years (later reduced to five years). This opened the door for many children of immigrants, who at the time were mainly guest workers from Türkiye and Eastern Europe. According to the German Statistics Office, approximately 47,500 babies born to foreign parents received citizenship in 2024, while 100,000 did not.
The study found that boys who were born just after the cut-off date to qualify for citizenship integrated better with their peers. Both boys and girls are more likely to attend pre-school, make faster progress in primary school, and are more likely to study more difficult academic subjects in secondary school. Their crime rate is 70% lower, and their parents are more likely to speak German and be integrated into the local community.
Simone Schüler, a researcher at the German Youth Institute, said the impact of citizenship may be subconscious - young adults may not fully understand how it shapes their lives.
"We see it in their behavior, their decision-making, their educational choices and whether they choose to commit criminal acts," Schueller said. "I'm not sure they realize it themselves."
However, five years of legal residency for parents is still a high threshold. Lack of citizenship can have significant consequences for children who were born in Germany but do not qualify, according to Magdalena Benavente, a legal adviser to the Berlin Immigration Council, which advises families with immigration issues.
