The court made an important exception: It said the ban “may not be enforced against foreign nationals who have a credible claim of a bona fide relationship with a person or entity in the United States.”

In the unsigned opinion, the court said that a foreign national who wants to visit or live with a family member would have such a relationship, and so would students from the designated countries — Libya, Iran, Somalia, Sudan, Syria and Yemen — who were admitted to a U.S. university.