Funny story. Some students at Tulane University in New Orleans worked with some area lawyers to clarify the whole brothel law issue. At Tulane, most sororities have houses, but they're just social halls. Anyway, long story short, no one could find any evidence that the law even existed! Here's the url to the article that appeared in the Tulane Hullaballo with the whole story:
http://www.tulane.edu/%7Etuhulla/199...sororityx.html