It shall be unlawful for any milk producer to offer for sale or sell milk or milk products to an in-state licensee as defined in N.H. Rev. Stat. § 184:84 who does not possess a valid producer permit issued by the commissioner. However, producers located beyond the limits of routine inspection are exempt from this requirement; provided, the milk from said producers shall have been produced under provisions which are substantially equivalent to the requirements of this subdivision and rules adopted hereunder and are enforced with equal effectiveness as determined by an enforcement rating which has been conducted on such forms and in such a manner and by such milk inspectors.