N.H. Rev. Stat. Ann. § 622:36

Upon the termination of any contract entered into in accordance with the provisions of this subdivision, or when the terms of any such contract shall so provide, convicts confined in county prison facilities or out-of-state institutions shall be returned by the commissioner of corrections or his assistant to the state prisons or shall be delivered to such other county prison facility or out-of-state penal institution as the commissioner of corrections shall have contracted with under the provisions of this subdivision. The commissioner of corrections shall provide for the return to this state of all such convicts as shall desire to return upon the expiration of their sentences or other discharge by law.