A federal court could rule as early as this week on the American Civil Liberties Union’s request for an injunction to stop the practice of splitting up migrant parents and children seeking asylum at the U.S. southern border.

The ACLU is asking U.S. District Judge Dana Sabraw in San Diego for a court order that would require Homeland Security officials to keep detained parents and children together in family facilities unless the government can show that the parents are unfit or pose a danger to their kids. The judge is expected...