Every person who unloads any farm product in a market and who is a registered unloader shall register his name, Federal Social Security number, and address and union affiliation, if any, with the commissioner. The commissioner shall supply each registered unloader with a card of registration. Each registered unloader shall carry such card at all times while employed or seeking employment in unloading any farm product in a market. A person within the definition of the term registered unloader shall not unload any farm product in a market unless he is registered as provided in this chapter.