31 CFR §552.405

1. (a)The prohibitions on transactions contained in § 552.201 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. (1)On behalf of or for the benefit of a person whose property and interests in property are blocked pursuant to § 552.201; or
   2. (2)With respect to property interests of any person whose property and interests in property are blocked pursuant to § 552.201.
2. (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 person whose property and interests in property are blocked pursuant to § 552.201.