I don't like much those threads usually, with a one line question leading to poor answers most of the time...

But here the question is interesting in its contruction and raises what's the main strength of btc that lots of old people can't understand!
You're asking if btc is legitimate or illegal. So you state that legitimate is more or less the contrary of illegal. But fact is that LEGAL and LEGITIMATE are different words for a reason ^^
Something can be illegal AND legitimate and that's mainly what bitcoin is! Or at least what the use of btc as a currency is.

Tons of governments are trying to ban btc as a currency and it is seldom recognized as a "real" currency. But fact is that a currency gains its legitimicy not from laws or rules, but from the use people make of and the trust they have in it.
A dollar in itself is nothing! It represents nothing and doesn't have any meaning. But people accept a dollar because they KNOW other people will also accept dollars and give them roughly the same value. Which is a dollar.

BTC si the same, governments and rules and laws can say wahtever they want but people accept a bitcoin because they know other people will accept the bitcoin and will give them, normally, roughly the same value. And most of them excpect in fact that once they'll try to give their btc for something else (currency, objects...) the value will have rise in fact xD

That's my 2cents on the subject, which is not as easy as it seems