(1)    Prohibition. Except as provided in sub. (1m), no person engaged in the business of buying milk from producers for the purpose of manufacture, processing or resale may discriminate between producers in the price paid for milk or in services furnished in connection with the purchase of milk if the discrimination injures producers or injures, destroys or prevents competition between competing purchasers of milk.

   (1m)   Milk pricing. A person engaged in the business of buying milk from producers for the purpose of manufacture, processing or resale may pay producers different prices for the purchase of milk based on differences in milk quality, if all of the following apply:

      (a)    Before making any payments to producers, the person engaged in the business of buying milk from producers establishes a payment method based on differences in milk quality determined by an actual measured difference in bacteria count, somatic cell count, enzyme level or drug residue findings in the milk.

      (b)    Before making any payments to producers, the person engaged in the business of buying milk from producers announces, and offers to make payments in accordance with, the payment method established under par. (a) to all producers from whom the person buys milk.

      (c)    The person engaged in the business of buying milk from producers makes payments to all milk producers from whom the person purchases milk in accordance with the payment method established under par. (a).

      (d)    The payment method established under par. (a) is not part of any other method used to discriminate between producers in the price paid for milk or in services furnished in connection with the purchase of milk.

   (2)   Contracts void. A contract in violation of this section or a special order issued under this section is void.

   (3)   Justification defense. It is a defense to a prosecution for violation of this section or a special order issued under this section to prove that the discrimination in price or services was done in good faith to meet competition or was commensurate with an actual difference in the quantity of or transportation charges or marketing expenses for the milk purchased.

   (4)   Enforcement.

      (a)    The department may, after hearing, issue a special order enjoining violations of this section.

      (b)    The department may, without alleging or proving that no other adequate remedy at law exists, bring an action to enjoin violations of this section or a special order issued under this section in the circuit court for the county where the alleged violation occurred.

   (5)   Penalties.

      (a)    A person who violates this section shall forfeit not less than $100 nor more than $2,500.

      (b)    A person who violates a special order issued under this section shall forfeit not less than $200 nor more than $5,000.