Avoid talking about \"legal\" issues directly: in one hand, the classification/legal status of Bitcoin can vary not only from country to country, but even between different regions/states within the same country.

Try to use instead:

Is bitcoin legal tender

...in this way you will capture the same semantic intent of the people searching for \"is bitcoin legal\", and it will be easier to write ever green content that is always compliant with local laws and remain relevant no matter the changes in regulations

so for instance, if you talk about \"legal tender\" you can approach the subject from the perspective of \"user adoption\" and talk about bitcoin increasingly becoming an accepted form of payment across the world, and how even large financial institutions are now investing into custodial solutions to have bitcoin in their own treasury.

Bitcoin History (Team Map)