With the limited number of actual avenues in Iran to which a bitcoin user can trade his bitcoins for cash, I can say that the ban of LocalBitcoins is somewhat already a hard blow. Well from the looks of it, it seems like this is just another one of the crazy tricks the US can look pull off to pin Iran on the wall pretty hard. Perhaps it is time for the Iranians to create their own exchange and figure out things from there.
They banned in due to risk factor of funds moving illegally for illegal purpose, so to stop it they have issued this notice.
Pretty sure it's more than that.