As far as I know, not all of countries, some of them legalized bitcoin, some don't, and the rest don't legalized it nor banned bitcoin. But, yes. when it's legal, taxes are there to be paid, since the regulator needs money too. 
So, if people wondering whether bitcoin legal or illegal, it depends on where she/he is, isn't it? So, it's important to find out the status in your own country.