Burt and Sally entered into a valid written contract for Burt to buy 1,000 bottles of 13 mg/ml e-liquid from Sally. E-liquid was the fluid that fueled electronic cigarettes (e-cigarettes). The mg/ml measurement specified the amount of nicotine in the fluid. Sally was a supplier of e-liquid. Burt operated an e-cigarette store. The contract called for delivery one month after the contract was signed and payment to be made at delivery. Two weeks after the contract was signed, Sally delivered to Burt 1,000 bottles of e-liquid. Burt noticed that 600 bottles contained 13 mg/ml e-liquid, while the remaining 400 bottles contained 11 mg/ml e-liquid. Burt rejected the 400 bottles of 11 mg/ml e-liquid and accepted the rest. The following day, the governor of the state in which Burt was located signed a law that banned the sale and purchase of all e-cigarettes, effective immediately. The development of the law had been covered in the news. Sally delivered to Burt 400 bottles of 13 mg/ml e-liquid two weeks after the first delivery. Burt rejected Sally's shipment and sought to return the first shipment of 600 bottles. Burt also refused to pay Sally. 

Discuss. Assume that issues of warranties do not apply.