31 CFR §583.412

1. (a)The property and interests in property of an entity, including any political subdivision, agency, or instrumentality of a governmental entity, are not blocked solely because one or more persons whose property and interests in property are blocked pursuant to § 583.201 is a member, leader, official, senior executive officer, or otherwise exercises control.
2. (b)For example, U.S. persons may not, except as authorized or exempt pursuant to this part, engage in the following transactions with a person whose property and interests in property are blocked pursuant to § 583.201: enter into contracts that are signed by a blocked person, enter into negotiations with a blocked person, or process transactions, directly or indirectly, on behalf of a person whose property and interests in property are blocked pursuant to § 583.201. However, U.S. persons are not prohibited from engaging in a routine interaction with an agency in which a blocked person is an official, but which does not involve the blocked person directly or indirectly.