(a) Except as permitted by law or by the rules in this subchapter, a warehouseman shall not deliver grain for which he or she has issued a negotiable receipt until the receipt has been returned to him or her and cancelled. He or she shall not deliver grain for which he or she has issued a nonnegotiable receipt until the receipt has been returned to him or her or until he or she has obtained a written order for the receipt from the person lawfully entitled to the delivery or his or her authorized agent.
(b) Before delivery is made of the last portion of a lot of grain covered by a nonnegotiable receipt, the receipt itself shall be surrendered.