Minors are supposed to take care and finish their studies first before joining any business ventures or trade but it hard to avoid that there are some business-minded minors that want to make some profits particularly in cryptocurrency trading. Some crypto exchanges have already stopped accepting minors like coinbase and bithumb and others might follow soon. But there are still no laws banning minors from using or investing in bitcoin or in any cryptocurrencies and they have the right to possess some amounts of bitcoin unless they use it in illegal activities.