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.
It seems to me that, Bitcoin legality is depend on the country. There has a country that Bitcoin is officially legal and they used it as a mode of payment, there are also a country who banned it officially and there is also a neutral between Bitcoin is not yet legal but you can used it. You are right about it depends on who you are using it and when you are using it. You will define the usage of Bitcoin.