Homeland Security officials can continue to waive environmental laws to speed construction of a fence on the U.S.-Mexico border, after the U.S. Supreme Court declined to hear an appeal by Defenders of Wildlife and the Sierra Club. The groups had argued that the eco-law-waiving power given to Homeland Security chief Michael Chertoff in 2005 was unconstitutional. The fence section named specifically in the lawsuit has already been built; it runs through Arizona’s San Pedro Riparian National Conservation Area, which is home to more than 250 species of migratory birds.