(a) It is specifically forbidden for any person knowingly to purchase or to authorize or requisition the purchase of beef other than beef raised and produced within the United States when such purchase is to be paid by the state government, any of its political subdivisions or any agency thereof out of public funds; provided, however, that the provisions of this subsection shall not apply to canned meat which is not available from a domestic source and which is not processed in the United States.
(b) Any purchase which is made in violation of the provisions of subsection (a) of this section shall be considered an illegal and unauthorized expenditure of public funds.