28 CFR 541.23: Administrative detention status.

You may be placed in administrative detention status for the following reasons:

(a) Pending Classification or Reclassification. You are a new commitment pending classification or under review for Reclassification.

(b) Holdover Status. You are in holdover status during transfer to a designated institution or other destination.

(c) Removal from general population. Your presence in the general population poses a threat to life, property, self, staff, other inmates, the public, or to the security or orderly running of the institution and:

(1) Investigation. You are under investigation or awaiting a hearing for possibly violating a Bureau regulation or criminal law;

(2) Transfer. You are pending transfer to another institution or location;

(3) Protection cases. You requested, or staff determined you need, administrative detention status for your own protection; or

(4) Post-disciplinary detention. You are ending confinement in disciplinary segregation status, and your return to the general population would threaten the safety, security, and orderly operation of a correctional facility, or public safety.