31 CFR § 536.406 - Provision of services.
(a) The prohibitions on transactions contained in § 536.201 apply to services performed in the United States or by U.S. persons, wherever located, including by a foreign branch of an entity located in the United States:
(1) On behalf of or for the benefit of a specially designated narcotics trafficker; or
(2) With respect to property interests of a specially designated narcotics trafficker.
(b) For example, U.S. persons may not, except as authorized by or pursuant to this part, provide legal, accounting, financial, brokering, freight forwarding, transportation, public relations, or other services to a specially designated narcotics trafficker.
See §§ 536.506 and 536.511 on licensing policy with regard to the provision of certain legal and emergency medical services.