19 CFR 103.33: Release of information to foreign agencies.

(a) The Commissioner or his designee may authorize Customs officers to exchange information or documents with foreign customs and law enforcement agencies if the Commissioner or his designee reasonably believes the exchange of information is necessary to—

(1) Ensure compliance with any law or regulation enforced or administered by Customs;

(2) Administer or enforce multilateral or bilateral agreements to which the U.S. is a party;

(3) Assist in investigative, judicial and quasi-judicial proceedings in the U.S.; and

(4) An action comparable to any of those described in paragraphs (a) (1) through (3) of this section undertaken by a foreign customs or law enforcement agency, or in relation to a proceeding in a foreign country.

(b)(1) Information may be provided to foreign customs and law enforcement agencies under paragraph (a) of this section only if the Commissioner or his designee obtains assurances from such agencies that such information will be held in confidence and used only for the law enforcement purposes for which such information is provided to such agencies by the Commissioner or his designee.

(2) No information may be provided under paragraph (a) of this section to any foreign customs or law enforcement agency that has violated any assurances described in paragraph (b)(1) of this section.