The United States Office of Foreign Assets Control (Ofac) can punish any individual or company that violates the US economic sanctions against a country, company or individual on which sanctions had been imposed by the US government, if the transactions involved were done in US dollars or through the US banks.
It is considered a violation to transact in the US currency, for instance, with countries such as Iran, Cuba and others subjected to blanket US sanctions.
Under the Electronic Code of Federal Regulations, in order to avoid violations, banks and firms have to comply with many laws. Those include the International Emergency Economic Powers Act, the Trading With the Enemy Act, the Foreign Narcotics Kingpin Designation Act and other statutes administered or enforced by Ofac.
The office also deals with presidential executive orders. According to an article published by Masuda Funai on Lexology.com, even for companies that utilise non-US banks, the possibility of US banks’ involvement in US dollar transactions is very high, since banks maintain foreign currency in accounts with “corresponding” banks in the country of that currency’s issuance.