A coalition of indigenous and environmental groups has filed a lawsuit against a planned pipeline that would carry oil from the Canadian tar sands to the United States. The suit comes less than two weeks after the State Department authorized the Alberta Clipper, a 1,000-mile pipeline running from Alberta to Wisconsin. Tar sand oil extraction is said to generate up to five times the greenhouse gas pollution of conventional oil. The lawsuit says the Obama administration has violated federal law by failing to properly gauge the pipeline’s environmental impact.