Three FBI agents specializing in counterterrorism, speaking on background to The Daily Beast, all shook their heads “no” when asked if a temporary immigration band would make their jobs any easier. Most of the credible ISIS cases the bureau has investigated, or the plots it’s been able to disrupt, have come from American-born suspects, one special agent told me.

A study of aspirational or successful ISIS attacks in the West between 2014 and 2015, most of them in the United States, certainly bears out this assessment.

Terrorism specialist Robin Simcox, formerly at the London-based Henry Jackson Society (where I also used to work) and now at the Washington, D.C.-based Heritage Foundation, counted a dozen ISIS plots in the United States between 2014 and 2015 (albeit before San Bernardino), some of them involving multiple suspects and all of them “inspired” by the jihadist organization rather than directly coordinated by it.

In only one instance, Simcox found, was a suspected terrorist not born in America, and in that instance she was longtime a U.S. citizen.