It is illegal in the US to use foreign currency because it is illegal to use any money that is not denominated in US Dollars.
Do you have a source for this claim, by chance?
Hi Stephen.
I've found that Paul Glover at Ithaca Hours, in Ithaca, New York, is a great source for accurate information on the law regarding US currency through his guide to creating local currency, which he sells. He was the first to answer this for me, about twenty years ago. Since then I've had it confirmed by the US Secret Service, which is the primary US government agency that deals with financial crime.
http://www.secretservice.gov/criminal.shtmlBy the way, I see you are online now and that you are a "hero", so perhaps you can answer my question by naming one nation that has ruled bitcoin either legal or illegal.