Why the Supreme Court’s birthright-citizenship decision may depend on the meaning of “domicile”

Immigration Matters is a recurring series by César Cuauhtémoc García Hernández that analyzes the court’s immigration docket, highlighting emerging legal questions about new policy and enforcement practices.

The future of President Donald Trump’s executive order attempting to limit access to birthright citizenship is now positioned for a final decision from the Supreme Court. Questioning from the justices, during approximately two hours of oral arguments in Trump v. Barbara, suggests an icy reception for the Justice Department’s claim that the constitutional guarantee of citizenship turns on an innovative interpretation of the legal concept known as “domicile.” Without acceptance of that interpretation by the court, the Trump administration is unlikely to successfully defend the president’s directive.

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Trump’s executive order, which he issued on January 20, 2025, claims that the 14th Amendment grants U.S. citizenship to children born in the United States depending on the citizenship or immigration status of their parents. The amendment’s citizenship clause provides that a person becomes a citizen “of the United States and the state wherein they reside” if they are born in the United States and are “subject to the jurisdiction thereof.”

To successfully defend the constitutionality of Trump’s order, U.S. Solicitor General D. John Sauer will have to convince a majority of justices on three fronts. First, that “subject to the jurisdiction thereof” means a person is “domiciled” in the United States. Second, that domicile should be interpreted to require legal permission to live in the United States indefinitely as a permanent resident, the most privileged form of immigration status, rather than temporarily or altogether without the federal government’s permission. Third, that children born in the United States acquire citizenship at birth only if their mother was domiciled in the country at the time of the child’s birth.

The text of the citizenship clause does not use the term domicile, but the Trump administration argues that it is implied. Sauer, who is the federal government’s lead attorney before the Supreme Court, argued that “reside,” which does appear in the citizenship clause (in terms of state citizenship), “means domicile in the Constitution.” For children to acquire U.S. citizenship at birth, the constitutional provision “presupposes domicile,” he told the justices. Though none of them openly embraced Sauer’s effort to read domicile into the 14th Amendment, none explicitly rejected his argument either.

Where several justices instead displayed skepticism was in the government’s proposed definition of domicile. The term generally refers to where a person lives and intends to continue living. As the court explained in a 1983 decision, domicile describes a person’s “permanent home and place of habitation. It is the place where he intends to remain, and to which he expects to return when he leaves.” This broad definition emphasizes an individual’s decision to make that person’s home in a particular location and continue doing so into the future. By contrast, Sauer claimed that domicile requires legal permission to live in a particular location, and that permission is dictated by immigration law. As he told the justices, domicile “is lawful presence with the intent to remain permanently.”

During oral arguments, several of the justices signaled their disagreement with Sauer’s definition of domicile. Without mentioning a lawful-presence component, Justice Samuel Alito stated that “a person’s domicile is the place where he or she intends to make a permanent home.” Meanwhile, Justice Neil Gorsuch seemed to directly reject Sauer’s inclusion of a lawfulness requirement. Gorsuch suggested that the legality of a person’s presence in the United States is irrelevant to domicile because in 1868, when the 14th Amendment was added to the Constitution, there were few federal laws regulating migration. Unlike today, when a complex series of federal immigration laws impose stringent restrictions on migrants and prospective migrants, “we really didn’t have laws like that” in 1868, Gorsuch told the solicitor general, “so why wouldn’t we, even if we were to apply your own test, come to the conclusion that the fact that someone might be illegal is immaterial”?

Sauer disagreed, arguing that the citizenship clause incorporates immigration restrictions enacted by Congress. Justice Ketanji Brown Jackson also clearly took issue with this claim. According to Jackson, the 14th Amendment was added to the Constitution “to prevent future Congresses from being able to affect citizenship.” (Sauer responded just as plainly, saying, “no, I don’t think so.”)

Whatever definition of domicile the justices accept, if they agree with the Trump administration that domicile is a required component of birthright citizenship’s constitutional analysis, they will need to then address whose domicile matters. No one disputes that domicile requires assessing where a person chooses to live, so it’s not surprising that they also agree that a child who is too young to decide where to live can’t form a domicile. Instead, a child’s domicile necessarily depends on a parent’s domicile. Responding to questions from Gorsuch, Sauer argued that historical sources don’t distinguish “between mother or father.”

There are two problems with Sauer’s claim that domicile doctrine treated mothers and fathers equally. First, it conflicts with Trump’s own executive order, which emphasizes the mother’s immigration status. According to the president’s interpretation of the 14th Amendment, a child born in the United States does not acquire citizenship at birth if the mother was not domiciled in the United States because she was living in the country unlawfully or with temporary authorization. Sauer likewise claimed that “it’s really the mother’s domicile, I think, that would matter.” Second, Sauer’s assertion at oral arguments clashes with the Justice Department’s written argument. Swiss jurist Emmerich de Vattel, whose The Law of Nations the government discusses repeatedly in its brief, left no doubt that legal doctrine treated the father’s status as more important than the mother’s. As Vattel explains in a section that the Justice Department’s brief cites, “children follow the condition of their fathers.”

Thus, the administration faces an uphill battle. It must not only convince the court to adopt its definition of domicile, but convince a majority of justices that the mother’s domicile is what counts despite no mention of this in the 14th Amendment. The oral argument suggests the government won’t succeed. But we will only know for sure when the court releases its opinion, which likely won’t be before late June.