The Collaborative International Dictionary of English v.0.48:

Maine \Maine\ (m[=a]n), prop. n.
   One of the New England States.
   [1913 Webster]

   Maine law, any law prohibiting the manufacture and sale of
      intoxicating beverages, esp. one resembling that enacted
      in the State of Maine. At present, the state of Maine
      sells such beverages in its own stores.
      [1913 Webster +PJC]