Home as a Question of Fact: Habitual Residence in International Law

In ordinary language, a dwelling is a place where someone lives. Law has always needed something more precise, because legal systems have to decide whose rules apply when a person's life touches more than one country. Lawyers call the link between a person and a legal system a connecting factor, and for most of modern history there were two main candidates.

The first was nationality: you are governed by the law of the state whose citizen you are. The second was domicile, a concept developed in common law systems, which generally asks where a person has their permanent home and, crucially, where they intend to stay. Domicile is intention-heavy. A court assessing domicile typically looks for a settled purpose of remaining, and a person does not easily lose an old domicile or acquire a new one. A Canadian court, for example, has described the change of domicile as requiring proof of a fixed and settled purpose to abandon the former one.

Habitual residence emerged as an alternative that would be simpler, more factual, and easier to apply across legal traditions. The Hague Conference on Private International Law pioneered its use as a connecting factor in its 1902 Convention on Guardianship and has used it in many conventions since. Its appeal, according to scholars who have traced the history, was that it appeared to be a straightforward factual concept, in contrast with the technical legal rules that surround nationality and domicile. The explanatory report to the Hague Conference's 1961 convention on the protection of minors described it as a question of pure fact, unlike domicile. One well-known law review article asked, in its title, whether habitual residence had become the new domicile.

The striking feature of habitual residence is how little the treaties say about it. The 1980 Hague Convention on the Civil Aspects of International Child Abduction, the instrument that gave the concept its greatest practical importance, does not define it. The same is true across the other Hague family conventions and of the European Union regulations that use the term. EU private international law relies on habitual residence as a widely used formula without an explicit legislative definition.

This was not an oversight. The drafters of these instruments generally regarded habitual residence as a question of fact to be settled case by case, and a fixed definition would have cut against that idea. The cost of that choice is that courts in different countries have had to supply the content themselves, and they did not always arrive at the same answer. As one comparative review put it, habitual residence can appear a very flexible connecting factor in some countries and a much more rigid one, closely tied to long-term residence, in others.

The traditional intuition remains useful in at least one respect: a person can have only one habitual residence at a time, and to acquire a new one a person must lose the old one. That "one place at a time" rule is what makes habitual residence workable as a way of assigning cases to courts.

To see why the definition matters so much, consider how the Hague Child Abduction Convention works. It was adopted in 1980 to address the problem of international child abductions during domestic disputes. By the time the United States Supreme Court decided its leading case on the subject in 2020, one hundred and one countries, including the United States and Italy, were parties to the Convention.

The Convention's central rule is that a child wrongfully removed from, or retained outside, the country of habitual residence must ordinarily be returned to that country. The decision on custody is then left to the courts of that country. Habitual residence therefore does two jobs at once. It identifies which country's courts are the proper forum for the custody dispute, and it defines what counts as "wrongful" removal in the first place. If the child's habitual residence was in Italy, taking the child to the United States without agreement is wrongful; if it was already the United States, the Convention may not apply at all.

That is why a single factual finding can decide the outcome of a case. Courts do not weigh who is the better parent at this stage. They ask where the child was living, and the answer determines where the real fight takes place.

Once courts had to decide what habitual residence actually means for a child, two broad schools emerged.

One school focuses on parental intention. In its most influential form, associated with the United States Court of Appeals for the Ninth Circuit in Mozes v. Mozes (2001), a child's habitual residence is usually not changed unless the parents share a settled intention to abandon the old residence and adopt the new one. The logic is that a young child cannot choose a home, so the shared purpose of those who control the child's life matters most. The Second and Seventh Circuits approved the Mozes approach. In Ruiz v. Tenorio (11th Circuit, 2004), a family kept a United States habitual residence despite a stay of roughly thirty-two months in Mexico, because the parents' plan was not to settle there permanently.

The second school looks at the child's actual life. This child-centered or acclimatization approach asks where the child has been living, in what environment, with what ties, and treats the parents' intentions as only one factor, and often a less important one. The Sixth Circuit advocated strongly for it. Other jurisdictions went further in this direction. The Supreme Court of Finland, in a 2011 case involving children taken between Finland and Scotland, held that habitual residence is where a person actually lives and where their main environment is located, with intention relevant but of less weight. The Supreme Court of Austria has said that a stay of more than six months will ordinarily amount to habitual residence. A majority of the New Zealand Court of Appeal specifically rejected the requirement of a settled intention to abandon the existing habitual residence.

The practical consequences of the split were sharp. A parent who agreed to a "trial year" abroad could find that, under an intention-based test, the child had never left the home country, while under a child-centered test the child might already be habitually resident in the new country. Forum shopping and strategic behavior followed from the uncertainty.

The Court of Justice of the European Union supplied one of the most influential formulations, in cases arising under the Brussels IIa Regulation on jurisdiction in matters of parental responsibility. In A (Case C-523/07, 2009) and Mercredi v. Chaffe (Case C-497/10 PPU, 2010), the Court held that a child's habitual residence corresponds to the place that reflects some degree of integration by the child in a social and family environment.

The Court listed the kinds of evidence that matter: the duration, regularity, conditions, and reasons for the stay in a member state and for the family's move there; the child's nationality; the place and conditions of school attendance; language skills; and the family and social relationships the child has in that state. Two points in particular have shaped later case law. First, full integration is not required, only a degree of it. Second, the child's age changes the analysis. For an infant, the social environment is essentially a family environment, defined by the people who actually care for the child. In Mercredi, which involved a baby taken from England to the island of Réunion, the Court explained that where the infant is looked after by her mother, the mother's integration in her own social and family environment becomes relevant, including why she moved, the languages she knows, and her geographic and family origins.

The Court has also insisted on physical presence. A child cannot be habitually resident in a state in which the child has never been present, as the Court held in OL v. PQ (Case C-111/17 PPU, 2017). There, an Italian father and a Greek mother had lived together in Italy, and agreed that the child would be born in Greece, near the mother's family, and that the mother would then come to Italy with the baby. After the birth the mother decided to stay in Greece. The Court concluded that the situation could not be classified as a wrongful removal or retention of the child, because the child had never lived in Italy.

English law offers a useful case study in how a national court reshaped its own concept to match the international one. For adults, the traditional English test for ordinary residence came from R v. Barnet London Borough Council, ex parte Shah (1983), in which the House of Lords asked whether a person had adopted a place voluntarily and for settled purposes. For years, English courts imported that language into habitual residence cases involving children.

That fit poorly. A child usually has little choice about where to live and no settled purpose of their own. In Re A [2013] UKSC 60, the Supreme Court, with Lady Hale noting the awkwardness of applying the Shah language to a child, held that the Shah test should be abandoned for deciding a child's habitual residence, and that the concept should be interpreted consistently with the Hague Convention and the European regulation. The Court also showed a general disinclination to burden the factual concept with supplementary rules, and the older English rule that one parent could not unilaterally change a child's habitual residence was consigned to history in favor of a fact-specific inquiry.

A later Supreme Court judgment by Lord Wilson, in Re B [2016] UKSC 4, offered what has become the best-known image in the field. Habitual residence, he suggested, works like a see-saw: when a child gains a new habitual residence, the child loses the old one. The "modern concept" requires not full integration in the new environment but only a degree of it, which in some circumstances can develop quickly. English judges have used the see-saw metaphor extensively in later cases.

The United States had one of the most divided bodies of case law, and it was the Supreme Court's decision in Monasky v. Taglieri (2020) that brought the country into line with the prevailing international approach.

Michelle Monasky and Domenico Taglieri met and married in the United States and moved to Italy in 2013 because of Taglieri's employment. Their daughter was born in Italy, the marriage deteriorated, and Monasky took the infant to the United States. Taglieri petitioned an Italian court for custody and then sought the child's return under the Hague Convention. The central question was whether the infant could have a habitual residence in Italy when the parents had not reached an actual agreement to raise her there.

Writing for the Court, Justice Ginsburg held that a child's habitual residence depends on the totality of the circumstances specific to the case, not on categorical requirements such as an actual agreement between the parents. The opinion noted that the Convention does not define habitual residence and that the inquiry is fact-driven, guided by common sense. It explained that this approach was in accord with the decisions of courts in other countries that are parties to the Convention and promoted the uniform international interpretation the treaty requires. For an infant, the Court recognized, the parents' intentions and circumstances are relevant but do not reduce to a single dispositive factor.

The Court also decided how appellate courts should review these decisions. A trial court's habitual residence finding is a mixed question of law and fact, though only barely so, and it is reviewed on appeal for clear error. Justice Thomas, concurring in part, described habitual residence essentially as the child's home: the place where the child has lived for an extended period, unless the presence was meant to be merely temporary.

The decision was widely understood as moving the United States closer to the European and Commonwealth view, and it came in a case that raised a sensitive point: the line between international child abduction and flight from domestic violence. The Convention contains an exception, Article 13(b), allowing a court to refuse return where it would expose the child to grave harm or an intolerable situation, and that exception is where concerns about abuse are usually addressed, rather than in the habitual residence inquiry itself.

Although children dominate the case law, habitual residence is used far more broadly. In the European Union it appears in regulations on divorce jurisdiction, maintenance, succession, and the law applicable to non-contractual obligations such as torts, where Article 23 of the Rome II Regulation addresses how it is applied to individuals and businesses. The Brussels IIb Regulation, which replaced Brussels IIa in 2022, continues to use it as the main basis of jurisdiction in divorce and parental responsibility cases.

For adults, the Court of Justice has articulated a two-part test. It looks first to the intention of the person to establish the habitual centre of his or her interests in a particular place, and second to a presence in the state concerned that is sufficiently stable. That formulation, applied in cases such as IB v. FA (Case C-289/20), on the law applicable to divorce, and MPA v. LCDNMT (Case C-501/20), keeps intention in the picture for adults, where the person can actually choose a home, while still insisting on factual presence. It is closer in spirit to the old English Shah test than the child-focused tests are, and it shows why the same words can mean subtly different things depending on whose life is being assessed.

Habitual residence has been criticized from several directions. Scholars have written of "habitual problems" in applying the concept to children, noting that even in the United Kingdom, which has had repeated appeals on the subject, courts continue to grapple with it. The flexibility that made the concept attractive makes outcomes harder to predict. Parents and lawyers cannot always know in advance whether a period abroad will be treated as a temporary stay or as the creation of a new home. Critics also worry that a purely factual test can be manipulated: a parent who relocates a child abruptly can try to create facts on the ground.

Defenders respond that every attempt to replace the flexible test with bright lines has run into hard cases that the lines handle badly: infants, children who have never lived in either claimed country, families who move repeatedly, parents who disagree about the move. A fact-sensitive standard, anchored by a settled set of factors, at least asks the right question, which is where the child's life actually is.

What the concept ultimately shows is a view of what makes a place a home. A legal address, a nationality, a passport, or a lease does not decide it on its own. The law asks about continuity, about relationships, schools, language, routines, and the degree to which a person has become part of a community. In other words, it asks about the lived reality of a dwelling. A dwelling in this sense is not a structure but a pattern of life, and the idea that courts across very different legal traditions have converged on that notion, with all their disagreements about details, is one of the more quietly remarkable achievements of modern private international law.