The Office of Foreign Assets Control

This is the part of the U.S. government that puts me in prison for ten to thirty years and makes me pay a ten million dollar fine for doing business with anybody in a country that has been sanctioned; Iran, Sudan, Cuba, Burma and N. Korea.  I have students in those countries!  If I taught English to people in those countries for free would I be in violation of some law?  Is communicating now a crime?  I would never work for free but I get the feeling that it's a criminal act to use my own language and that big brother is watching me just to make sure I don't stray from the straight and narrow.