At least when I lived there Louisiana had pretty much the same law as Alabama.  The law allowed transport across the state and the importation of bees only on new equipment.  As far as the history of this law it was more about the concerns that Randy Oliver suggest (crowding out of existing native beekeepers) than anything that has to do with pest or pathogen.  Basically there is a small strip of geography in the very southern part of the state that was premier queen rearing area.  This basically works out that if you wish to take up queen rearing there you pretty much are forced to buy out an existing beekeeper. 

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