If he acquired them legal of course he can sell them an get fiat withdrawn to his bank, assuming hes not in a place where bitcoin is illegal. Doing this all at

If he acquired them legal of course he can sell them an get fiat withdrawn to his bank, assuming hes not in a place where bitcoin is illegal. Doing this all at once without informing your bank will probably instantly freeze the funds and trigger some kind of investigation. That doesn't mean you eventually get access to it. Also there are exchanges withdraw limits so its not on your bank account in 1-2 working days. If you want to sell all at once and withdraw you would have to register on different exchanges to circumvent daily limits and do the KCY which that can take days to get verified.