Native American and environmental groups filed suit Thursday in federal court in San Francisco challenging a proposed tar sands oil pipeline that would bring the dirtiest oil on Earth from Canada to the United States.

The U.S. State Department’s approval on Aug. 20 of Enbridge Energy’s Alberta Clipper pipeline permits 450,000 barrels of tar sands oil per day to be pumped from northern Alberta to Superior, Wis., for refining.

Tar sands oil is dirtier and, over its lifecycle, emits more global warming pollution than any other type of oil. Tar sands development in Alberta is creating an environmental catastrophe, with toxic tailings ponds so large they can be seen from space, and plans to strip away forests and peat lands of an area the size of Florida.

"The Alberta Clipper will mean more air, water and global warming pollution, particularly in communities near refineries that process tar sands oil," said Earthjustice attorney Sarah Burt in a press release. "The State Department fails to show how building a pipeline to import the dirtiest oil on Earth is in our national interest.”

You can download the complaint here.See more photos of the devastation of tar sands at www.dirtyoilsands.org.