Certainly if someone is on the terrorist watch list, requiring a WBI screening should be standard procedure.

CNN: Don't let security scanners erase our privacy

The Bush administration formally refused the Canadian government's request to remove Maher Arar from a terrorist watch list.

NPR: U.S. Denies Canada's Terror Watch-List Request

Counterterrorism officials have reviewed and updated our terrorist watch list system, including adding more individuals to the "no fly" list.

WHITEHOUSE: President Obama Speaks to the Press After Security Meeting