It is a relative new law (5-10ish years) called something like "anti-terrorism funding and money laundering law". It require the bank teller to inquire the nature of any withdraw or transaction, and the power/requirement to stop any money withdraw or transaction in case the teller aren't satisfied with the answers the customer gave.

All to the discretion of the bank. No criminal investigation is needed to stop transactions/withdraws. They might not be able to close the account, but they can prevent any money from being removed from it as long they like.

It's also the same law that are currently is preventing unregistered phones from using sms-purchase for tickets to buses and trains. The law directly forbids any kind of money transfers if one of the participants are not directly identified.