31 CFR §549.405

1. (a)Except as provided in § 549.206, the prohibitions on transactions involving blocked property contained in § 549.201 apply to services performed in the United States or by U.S. persons, wherever located, including by an overseas 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 § 549.201(a); or
   2. (2)With respect to property interests subject to § 549.201.
2. (b)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 § 549.201(a).