What does the term ‘prohibited transaction’ mean?

OFAC Attorney: Prohibited transactions are trade or financial transactions and other dealings in which U.S. persons may not engage unless they are authorized by OFAC or are expressly exempted by statute. Because each sanctions program is based on different foreign policy and national security goals, the prohibitions may vary between the programs.  These variations can even exist when interpreting the same regulatory language across different sanctions programs.  This is one of the reasons it is important to speak with an experienced sanctions attorney before speaking with OFAC.