If you live in the US, can you pay your taxes with Euros? Most would argue that Euros are money, yet you cannot pay your taxes with them.
If you live in the US, Euro is a foreign currency only, not money.
It's still money. Just because it's a foreign currency doesn't mean someone cannot accept it. It's still wealth. Some coiuntries even accept many other currencies from around the world. Some countries in Africa actually prefer dollars or euroes to their own fiat.
Bitcoins, gold, silver and foreign currencies can be used like money, they have the properties of money, but they are not money, since money is something enforced by a government power.
That might be the definition of legal tender, but foreign currency is still money. Besides, I think the very definition of what is money has changed or at least evolved with bitcoin. Bitcoin is money to me regardless of a government not issuing it. It's still issued by the bitcoin software and issued fairly at that.