Not just because the U.S. ambassador says not too. But because deciding on the "safest route" in an EIS (Environmental Impact Statement) is just a matter of counting how many streams must be crossed, properties expropriated, and etc, and assigning a score.. I would argue, and have argued, that by this measure the route already rejected was the safest one available (had the best score), and that any rejig:
...simply transfers the environmental risk to some place other than Sandhills, and increases it overall. If the Obama administration can't get behind the current route, it would be even more difficult to get behind any of its major competitors. And note too that Nebraska lawmakers themselves are only talking about moves that would increase the pipe length by 30 or 40 miles, which doesn't sound like any of the possibilities considered in the EIS and which, therefore, will almost certainly not solve the problem of the pipe's crossing Nebraska's environmentally sensitive areas in the first place.
Plus the oil companies just spend $1,000,000,000s to defeat Obama. He owes them dick.