WASHINGTON (AP) — The Supreme Court has delivered a setback to Montana homeowners who are seeking additional cleanup of arsenic left over from years of copper smelting.

The court said Monday that the homeowners cannot proceed with efforts to decontaminate their own property near the shuttered Anaconda smelter without the permission of the Environmental Protection Agency.

The smelter belongs to BP-owned Atlantic Richfield Co. and sits at the center of a 300-square-mile Superfund site.

The company says it has spent $470 million to clean the site.

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