Have you seen this news story?
Basically, Jason Rezaian, a dual Iranian and American citizen, has been detained for eight weeks in Iran. No charges have been announced against him, which is in keeping with the way Iran treats its citizens. And there is nothing that the United States can really do, other than ask Iran to release him.
This is just a quick reminder, since dual citizenship is so rarely in the news, of what it means and the potential bad consequences, in the case of a dual citizen of Iran and the U.S. When you are in one country of which you are a citizen, that country will treat you only as its citizen, and totally ignore the claim any other country may have on you. And there is essentially nothing your "other" country of citizenship can do to help you, if you get in trouble.
Being a citizen of Iran, this journalist is an Iranian when he is in Iran and an American when he's in America. Just as the U.S. ignores the Iranian citizenship of dual citizens when they are in the U.S., so Iran ignores the U.S. citizenship of its citizens when they are in Iran. It's safe to say the justice system there is not what we would expect in the U.S.A.
Be careful with those passports and where you travel on them.