Okla. Stat. tit. 12A, § 12A-2-615: Excuse by Failure of Presupposed Conditions

Except so far as a seller may have assumed a greater obligation

and subject to the preceding section on substituted performance:

(a) Delay in delivery on nondelivery in whole or in part

by a seller who complies with paragraphs (b) and (c) is not a breach

of his duty under a contract for sale if performance as agreed has

been made impracticable by the occurrence of a contingency the

nonoccurrence of which was a basic assumption on which the contract

was made or by compliance in good faith with any applicable foreign

or domestic governmental regulation or order whether or not it later

proves to be invalid.

(b) Where the clauses mentioned in paragraph (a) affect

only a part of the seller's capacity to perform, he must allocate

production and deliveries among his customers but may at his option

include regular customers not then under contract as well as his own

requirements for further manufacture. He may so allocate in any

manner which is fair and reasonable.

(c) The seller must notify the buyer seasonably that there

will be delay or nondelivery and, when allocation is required under

paragraph (b), of the estimated quota thus made available for the

buyer.