I don't believe banks banning crypto purchases should be legal by any means but I don't believe that there is anything wrong with credit cards charging a cash advance for crypto purchases. You can still use debit and checking to buy without an additional fee, if a bank or credit card bans that part I don't believe anyone should remain a customer, but if crypto is truly currency then paying with a credit card just makes it a cash advance. I know it's not a popular opinion but you can't want to make a currency but also not treat it as currency.