I think the word "currency" is just a construct of language derived from usage by people. That's why Bitcoin already is a currency (i.e. a crypto-currency) and it doesn't need any entity to authorize its existence (because it already exists).

What you might be wanting to know if it has been declared "legal tender" in any country and I am 99% sure it has not. The irony, though, is that most people don't have a clue what the term "legal tender' means in a legal sense.

I don't think Bitcoiners would generally like the idea of Bitcoin usage being forced upon anyone (that is what "legal tender" laws accomplish).