A Colorado city’s attempt to ban hydraulic fracturing conflicts with the state’s authority and is invalid, a district court judge ruled Thursday. My colleague Cathy Proctor at the Denver Business Journal reports that Judge D.D. Mallard granted a summary judgment that enjoins the city of Longmont from enforcing its voter-approved ban on fracking. Lawyers and oil and gas executives are warning that a similar drama could play out here in Denton, where voters will consider a fracking ban on Nov.…