In principle, the court of the country where the child is habitually resident when proceedings begin, rather than the country of the parents’ nationality.
If the child lives in an EU Member State other than Denmark, that State’s courts have jurisdiction (Brussels II ter Regulation, Article 7). After a lawful move to another Member State, the courts of the former residence retain jurisdiction for three months to modify contact arrangements (Article 8). Under certain conditions, parents can also choose the courts of a State with which the child has a close connection (Article 10).
If the child lives in a State party to the Hague Convention of 19 October 1996, the authorities of that State have jurisdiction (Article 5).
Elsewhere, the French court applies national rules (Article 1070 of the Code of Civil Procedure and, as a last resort, the French nationality of a parent under Articles 14 and 15 of the Civil Code). Its decision may nevertheless not be recognized where the child lives.
In urgent cases, courts where the child is present may take provisional measures (Brussels II ter, Article 15; 1996 Convention, Article 11). Habitual residence is a factual question involving the duration and regularity of the stay, schooling, and family and social connections. It requires evidence and can be disputed.