It’s been all over FR I think, hang on. Here are some other sites:
http://www.allgov.com/Unusual_News/ViewNews/Louisiana_Bans_Using_Cash_for_Sales_of_Second_Hand_Goods_111022
http://www.techdirt.com/articles/20111019/17424316421/louisiana-makes-it-illegal-to-use-cash-secondhand-sales.shtml
http://www.forbes.com/sites/kenfisher/2011/10/21/louisianas-poor-hating-politicians-cash-bashing-lindsay-lohan/
Insane. And if they think it will stop petty theft they are dreaming.