The Trump administration has cleared the way for a controversial project that would suck groundwater from under Southern California’s Mojave Desert and sell it to water providers. On Friday, the Bureau of Land Management wrote that Cadiz Inc.’s plan to build a 43-mile pipeline along a railroad right of way did not require the agency’s approval. The letter reverses the Obama administration’s opinion, which said in 2015 that the 1875 law governing the easement required that it be used for railroad purposes. Otherwise, it required federal approval.