28 CFR § 540.18 - Special mail.
(a) The Warden shall open incoming special mail only in the presence of the inmate for inspection for physical contraband and the qualification of any enclosures as special mail. The correspondence may not be read or copied if the sender is adequately identified on the envelope, and the front of the envelope is marked “Special Mail - Open only in the presence of the inmate”.
(b) In the absence of either adequate identification or the “special mail” marking indicated in paragraph (a) of this section appearing on the envelope, staff may treat the mail as general correspondence and may open, inspect, and read the mail.
(2)Special mail shall be screened in accordance with the provisions of paragraph (c)(2)(iii) of this section when the special mail is being sent by an inmate who has been placed on restricted special mail status.
(i) An inmate may be placed on restricted special mail status if the Warden, with the concurrence of the Regional Counsel, documents in writing that the special mail either has posed a threat or may pose a threat of physical harm to the recipient (e.g., the inmate has previously used special mail to threaten physical harm to a recipient).
(iii) An inmate on restricted special mail status must present all materials and packaging intended to be sent as special mail to staff for inspection. Staff shall inspect the special mail material and packaging, in the presence of the inmate, for contraband. If the intended recipient of the special mail has so requested, staff may read the special mail for the purpose of verifying that the special mail does not contain a threat of physical harm. Upon completion of the inspection, staff shall return the special mail material to the inmate if the material does not contain contraband, or contain a threat of physical harm to the intended recipient. The inmate must then seal the special mail material in the presence of staff and immediately give the sealed special mail material to the observing staff for delivery. Special mail determined to pose a threat to the intended recipient shall be forwarded to the appropriate law enforcement entity. Staff shall send a copy of the material, minus the contraband, to the intended recipient along with notification that the original of the material was forwarded to the appropriate law enforcement entity.
(iv) The Warden shall review an inmate's restricted special mail status at least once every 180 days. The inmate is to be notified of the results of this review. An inmate may be removed from restricted special mail status if the Warden determines, with the concurrence of the Regional Counsel, that the special mail does not threaten or pose a threat of physical harm to the intended recipient.
(d) Except for special mail processed in accordance with paragraph (c)(2) of this section, staff shall stamp the following statement directly on the back side of the inmate's outgoing special mail: “The enclosed letter was processed through special mailing procedures for forwarding to you. The letter has neither been opened nor inspected. If the writer raises a question or problem over which this facility has jurisdiction, you may wish to return the material for further information or clarification. If the writer encloses correspondence for forwarding to another addressee, please return the enclosure to the above address.”