They're "choking off the money supply that will choke off the terrorists." I guess they've established a stranglehold on Saudi bankbooks. From the [1] Washington Times, with thanks to Jeffrey Imm:

Terrorists looking to move millions of dollars out of the United States to fund global strikes have resorted to a kaleidoscope of new schemes aimed at hiding illicit cash, but one of the nation's top terrorism investigators says law-enforcement authorities are up to the challenge.

Marcy Forman, who supervisors 6,000 U.S. Immigration and Customs Enforcement (ICE) agents at 156 field and 52 foreign offices as head of the agency's Office of Investigations, said newly created law-enforcement partnerships are "choking off the money supply that will choke off the terrorists."