Regulations regarding taxes are absolutely the authority of the country where he lives. Maybe it will be different in some other countries. In my country, taxes are imposed on users who trade on centralized exchanges registered in our country. The tax fee is simultaneously deducted along with the trading fee and later the exchanges themselves deposit the tax to the state, from a certain percentage deduction. but when withdrawing it to a bank account, for now there is no tax, except if you regularly withdraw money with a high nominal, there may be something like income tax. And this may be different where your friend is, but if that country applies taxation to crypto, surely he has to pay those taxes, whether he likes it or not as long as he's doing the transaction.