Iran’s powerful RGC was initially established to serve as the vanguard of Iran's 1979 revolution.
It currently enjoys more autonomy than the rest of the Iranian military, answering only to Iran's supreme leader.
The RGC is also solely responsible for Iran's formidable ballistic missile program.
Monday's action by the U.S. opens the door for the potential criminal prosecution of individuals who do business with the RGC.
It could serve to hinder U.S. diplomacy, however, particularly in Iraq and Lebanon, where local officials are in regular contact with RGC representatives.