18 U.S. Code § 3623. Transfer of a prisoner to State authority
The Director of the Bureau of Prisons shall order that a prisoner who has been charged in an indictment or information with, or convicted of, a State felony, be transferred to an official detention facility within such State prior to his release from a Federal prison facility if—
the transfer has been requested by the Governor or other executive authority of the State;
the State has presented to the Director a certified copy of the indictment, information, or judgment of conviction; and
If more than one request is presented with respect to a prisoner, the Director shall determine which request should receive preference. The expenses of such transfer shall be borne by the State requesting the transfer.