A federal judge has found that part of a Minnesota law designed to promote the use of renewable energy is unconstitutional and she barred state officials from enforcing it. In a 48-page opinion, US District Judge Susan Richard Nelson said Friday that part of the Next Generation Energy Act improperly requires North Dakota utilities to seek approval from Minnesota in order to do business. Governor Dayton says he strongly disagrees with Nelson’s opinion and the state will appeal. North Dakota officials are calling the ruling a “vindication” – saying that North Dakota businesses shouldn’t have to ask Minnesota regulators for permission to operate. Among other things, the 2007 law bars utilities from buying power from new plants that produce carbon dioxide emissions.