N.H. Rev. Stat. § 21-H:12

I. The commissioner may transfer any inmate, provided that whenever a transfer involves a county facility, a contract specifying the conditions of that transfer shall have been executed in advance. II. A transfer may be made whenever the commissioner determines that an inmate cannot be properly or safely kept at the correctional facility at which he is confined or that such transfer is in the best public interest or furthers legitimate penological objectives. When any transfer involves a county facility, the commissioner of corrections shall obtain the approval of the appropriate county correctional administrator before making such a transfer.