Rep. Weldon today on one of the shows said that the President can send them in.
"Today, the Marshals Service is responsible for providing protection for the federal judiciary, transporting federal prisoners, **protecting endangered federal witnesses** and managing assets seized from criminal enterprises."
Santorum was asked about what is supposed to happen next, and he said that the US attorney is so far either unwilling or is refusing to enforce what congress has so far done. He's dragging his feet for one reason or another.
I just can't remember whether he said unwilling or is refusing.
I think he meant the US atty in Florida, but maybe someone else knows more.