If there are no such laws, it's completely legal, and since law doesn't work backwards, if it's ever outlawed, nobody will be able to prosecute you for using it in the past.
1) There are grey areas in law, subject to interpretation. The government may prosecute you based on current interpretation of law, for your past actions.
2) Some countries have enacted laws with
retrospective effect.
https://www.alrc.gov.au/publications/laws-retrospective-operation-0If the law to be enacted were to have a retroactive effect, then past actions such as possession and usage of bitcoin would be prosecuted.
Most jurisdictions do not specify and have yet to declare their legal stand on bitcoin. In the future perhaps, there will be stipulations made on the specifics for Bitcoin. Such as the situation in my country - since there are no laws that declare it as illegal, then the use of Bitcoin is not prohibited. They have not declared it as legal either, simply recognized by the central banking with a fair warning to the public for its usage.