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.
If in my country Bitcoin is not yet legalized, but the Government in my country still allow its citizens to have Bitcoin and only prohibit it to be used as a transaction tool. So Bitcoin is still legit in my country.
Here it is considered legal because there is no regulation stating that it is illegal, so we are free to do what we want for as long as we are not fooling people to do investment in it, or to make an investment scam because we do have law regulated for the protection of everyone especially investors.