No dealer shall receive or purchase milk from producers or others within the state for storage, manufacture, processing, sale, distribution or handling within or without the state, or sell or distribute milk within the state, unless such dealer is licensed as provided herein. No dealer shall buy milk from, or sell milk to, a dealer within the state who is unlicensed, or deal in or handle milk which he has reason to believe has previously been dealt in or handled in violation of this part or any order, ruling or regulation issued hereunder. The license period shall be for a period of two years and extend from July first to the second following June thirtieth, inclusive.