I followed the link trail and found this:
“The Dairy Stabilization Board oversees milk prices in Louisiana. The board was established after Schwegmann, a New Orleans-area grocery chain, launched a legal battle in the 1970s with the Louisiana Milk Commission to buy milk from out-of-state suppliers because it was cheaper.”
http://theadvocate.com/news/4992757-123/state-stops-sale-of-cheap
Just as I thought. The in-state milk industry used the courts and legislature to stifle competition........