A judge's decision Wednesday to overturn a Nebraska law that allowed the [Keystone XL] pipeline guarantees the legal fight will continue for at least several more months...The ruling was a victory for pipeline opponents, including environmentalists who say Keystone XL would carry "dirty oil" that contributes to global warming and Nebraska ranchers and farmers who fear it could hurt their water supply...[A] 2012 law that allowed Gov. Dave Heineman to approve the route through Nebraska...Three landowners filed a lawsuit saying the decision should have been made by the Public Service Commission. Lancaster County Judge Stephanie Stacy agreed...A spokesman for pipeline developer TransCanada said company officials were disappointed and disagreed with the decision...Randy Thompson, a Nebraska rancher and a leading plaintiff in the lawsuit, became involved in the dispute after he was notified that the original Keystone XL route would have crossed his parents' 400-acre farm in Merrick County. He said he doesn't think TransCanada should be able to force landowners to sign pipeline contracts using eminent domain.