Ark. Code Ann. § 23-37-508

An association or a federal association may recognize, or continue to recognize, the authority of an attorney in fact authorized in writing to manage or to make withdrawals, either in whole or in part, from a savings account until it receives written notice of the revocation of the authority of the attorney in fact or until it receives written notice of the death or adjudication of incompetency of the owner of the savings account.