28 C.F.R. § 541.40

(a) In an effort to maintain a safe and orderly environment within its institutions, the Bureau of Prisons operates control unit programs intended to place into a separate unit those inmates who are unable to function in a less restrictive environment without being a threat to others or to the orderly operation of the institution. The Bureau of Prisons provides written criteria for the:

(1) Referral of an inmate for possible placement within a control unit;

(2) Selection of an inmate for placement within a control unit;

(3) Regular review of an inmate while housed in a control unit; and

(4) Release of an inmate from a control unit.

(b) The Bureau of Prisons provides an inmate confined within a control unit the opportunity to participate in programs and activities restricted as necessary to protect the security, good order, or discipline of the unit.