So a member in good standing of the Nigerian economic and political elite contacts the US embassy in Yemen. He says his son has gone off the deep end, fallen in with radical jihadis, and has traveled to Yemen to link up with fellow combatants.
And what does the embassy do? They put the son’s name on a list with 550,000 others—people who have attracted suspicion for any reason and no reason, intellectuals or just ordinary people who have expressed ideas evoking the disapproval of US officials (think of Tariq Ramadan), and untold numbers whose names were flagged purely by profiling.
Of course, a list of 550,000 names is no list at all. You are not going to do expanded searches on all of them in airport security lines, nor run all their luggage past canine noses. No, they will just board the airplane, and you must hope for the best.