ON TUESDAY, U.S. authorities diverted a United Airlines London-Washington flight to Bangor, Maine, where the ex-pop singer formerly known as Cat Stevens, now as Yusuf Islam, was questioned by federal security agents, and then ordered deported back to Britain. Yusuf Islam, it turns out, is on the official “no-fly list.”

This action will doubtless provoke loud and prolonged guffaws from those who consider American security policies to be excessive. But a look at the career and associations of Yusuf Islam since he became a Muslim in 1977 shows that the decision was correct.