He's already been arrested and charged federally. This was just to preserve the right for the state to try him later, assuming they did so just in case he was aquitted of federal charges. Seems a rather standard kind of thing to do, no?
I doubt the feds will give up custody. I'm sure they've dusted a cell out for him at the Fed Super Max in Florence Colorado.. the final stop for crimes deemed to have reached a certain level of infamy and having a political character to them. 23 hours a day in solitary.. no interaction with other inmates.. no view of the mountains.