MADISON, Wis. (WTAQ) - The state has joined a lawsuit that tries to stop Dean Foods’ ownership of milk plants sold by Foremost Farms USA. Attorney General J.B. Van Hollen is joining his counterparts from Michigan and Illinois and the U.S. Justice Department in fighting the acquisition. It involves the sale of the bottling plants in De Pere and Waukesha. The officials say the deal violates federal law, because it reduces the competition for milk sales to schools in Wisconsin and elsewhere. But Dean says its ownership is not damaging to competition – and it helps Wisconsin dairy farmers by providing a stable and growing outlet for their milk. Dean also says the acquisition has produced cost savings that help customers, and promote retail competition.