The Supreme Court is slated to hear arguments today in a case that pits about 100 Montana residents against the oil giant BP — one of the largest companies in the world. The residents are demanding the Atlantic Richfield Company, which is owned by BP, clean up decades of arsenic pollution from a massive copper smelter. The company is arguing it is only required to clean up the site to Superfund standards. The case could have sweeping significance for other Superfund sites across the United States.