Who determines domicile: courts or Congress?

A case in which the Court will decide whether Executive Order No. 14,160 issued by President Donald, which denies U.S. birthright citizenship to children born in the United States solely because their parents are in the country unlawfully or on temporary visas, is consistent with the Citizenship Clause of the Fourteenth Amendment and 8 U.S.C. § 1401(a).