A public warehouseman license is not effective unless all grain in storage or on deposit in the warehouse is kept fully insured at the expense of the warehouseman for the benefit of the owner at the current market value of the grain against loss by fire, lightning, internal explosion, windstorm, cyclone, tornado, and other risks of direct physical loss as provided by the insurer in a policy approved by the insurance commissioner. An insurance policy covering grain in a public warehouse may not be transferred or assigned to any person for any purpose, except for grain that is not on warehouse receipt or deposit. The insurance policy must be continuous and may only be canceled in accordance with section 4.1-58-36.