Inmates of the penitentiary shall be confined in separate cells at night whenever there are sufficient cells. No communication shall be allowed between inmates of the penitentiary and persons without the penitentiary except under the supervision prescribed by the rules and regulations of the penitentiary. No person, without the consent of the warden, shall bring into or carry out of the penitentiary any writing or information to or from an inmate.
N.D.C.C. § 12-47-22