31 C.F.R. § 597.201 – Prohibited transactions involving blocked assets or funds of foreign terrorist organizations or their agents.

(a) Upon notification to Congress of the Secretary of State's intent to designate an organization as a foreign terrorist organization pursuant to 8 U.S.C. 1189(a), until the publication in the Federal Register as described in paragraph (c) of this section, any U.S. financial institution receiving notice from the Secretary of the Treasury by means of order, directive, instruction, regulation, ruling, license, or otherwise shall, except as otherwise provided in such notice, block all financial transactions involving any assets of such organization within the possession or control of such U.S. financial institution until further directive from the Secretary of the Treasury, Act of Congress, or order of court.
(b) Except as otherwise authorized by order, directive, instruction, regulation, ruling, license, or otherwise, from and after the designation of an organization as a foreign terrorist organization pursuant to 8 U.S.C. 1189(a), any U.S. financial institution that becomes aware that it has possession of or control over any funds in which the designated foreign terrorist organization or its agent has an interest shall:
1. (1) Retain possession of or maintain control over such funds; and
2. (2) Report to the Secretary of the Treasury the existence of such funds in accordance with § 501.603 of this chapter.
(c) Publication in the Federal Register of the designation of an organization as a foreign terrorist organization pursuant to 8 U.S.C. 1189(a) shall be deemed to constitute a further directive from the Secretary of the Treasury for purposes of paragraph (a) of this section, and shall require the actions contained in paragraph (b) of this section.
(d) The requirements of paragraph (b) of this section shall remain in effect until the effective date of an administrative, judicial, or legislative revocation of the designation of an organization as a foreign terrorist organization, or until the designation lapses, pursuant to 8 U.S.C. 1189.
(e) When a transaction results in the blocking of funds at a financial institution pursuant to this section and a party to the transaction believes the funds have been blocked due to mistaken identity, that party may seek to have such funds unblocked pursuant to the administrative procedures set forth in § 501.806 of this chapter. Requests for the unblocking of funds pursuant to § 501.806 must be submitted to the attention of the Compliance Programs Division.