British Muslims—including a family of 11 headed to Disneyland—are increasingly being barred from the U.S. without explanation, according to critics in the UK, who are calling on Prime Minister David Cameron to step in and address the problem.

Despite the family having been granted travel authorization online ahead of their planned December 15 flight to Los Angeles, the U.S. Department of Homeland Security refused to allow them to board the plane at London‘s Gatwick Airport. No one has told them why they were prevented from traveling.