They also don't allow any Bitcoin mined outside Iran to be used in their country, that is so stupid and ridiculous but other countries like China may follow something similar in future.
There is a difference between an actual law that is written somewhere and someone (even the government itself) saying something. And there is no law saying you can't use bitcoin that is mined outside Iran. They had a meeting in central bank and decided that there should be one but nothing has gone to congress to even be discussed let alone become law.
By the way the news was the opposite meaning you can't spend bitcoins mined inside Iran for anything other than import/export.