Indigenous and environmental groups are vowing to challenge an Obama administration decision to approve a pipeline carrying oil from the Canadian tar sands to the United States. Last week, the State Department issued a permit for the Alberta Clipper, a 1,000-mile pipeline running from Alberta to Wisconsin. Extracting oil from the tar sands is said to generate three to five times as much greenhouse gas pollution as the production of conventional oil. In a statement, the group Earthjustice said, “At a time when concern is growing about the national security threat posed by global warming, it doesn’t make sense to open our gates to one of the dirtiest fuels on Earth…This is exactly the kind of project the State Department should be protecting us from.”