[So we're technically saving money, right?]
Separate sovereigns.  The state and the federal government can both try them for various crimes.  IIRC, if convicted the accused would serve one sentence followed by another sentence by the other.  Also, that assumes the federal charges will even stick.  As above, it's pretty tenuous.
Though I still scratch my head at whether the defense attorneys are going to take the federal charges to task as it is probably too much of a toss-up on how the district judge would come down on it.  And I doubt the thieves have the money to run it up the appellate chain if they lose.