The legality of bitcoin depends on who you are, and what youre doing with it.
There are three main categories of bitcoin stakeholder. Someone may fall under more than one of these categories, and each category has its own legal considerations.
For me, Bitcoin cannot be said legal at all. Because I live in a country that has not legalized Bitcoin and is still very limited to use Bitcoin. But at least though I still use Bitcoin, the Government does not punish me and I'm safe to use Bitcoin all this time.