The U.S. Supreme Court handed BP Plc unit Atlantic Richfield Co a victory on Monday, making it harder for Montana landowners to seek a more extensive cleanup of a hazardous waste site than the federal government had ordered.

FILE PHOTO: The logo of BP is seen at a petrol station in Kloten, Switzerland October 3, 2017. REUTERS/Arnd Wiegmann

In a case involving the Environmental Protection Agency’s Superfund program responsible for cleaning up certain toxic waste sites, the justices threw out a state court decision that had allowed the claims for restoration damages by the private landowners at Atlantic Richfield’s former Anaconda copper smelter in western Montana to proceed to trial.

In the 7-2 ruling authored by conservative Chief Justice John Roberts, the court decided that under the law governing Superfund sites the property owners needed the EPA’s approval before undertaking restoration of their own contaminated land.

That system ensures the “careful development of a single EPA-led cleanup effort rather than tens of thousands of competing individual ones,” Roberts wrote.

In dissent, Justice Neil Gorsuch, joined by fellow conservative Justice Clarence Thomas, denounced the implication that property owners “cannot be trusted to clean up their lands without causing trouble.”

The case hinged on the scope of the Superfund law. The Superfund program, started in 1980, is intended to identify contaminated sites and ensure that those responsible for the pollution pay for the hazardous waste cleanup. It has been criticized over the years for slow cleanup efforts.

The decision represented a victory for companies like Atlantic Richfield and business groups that said the lower court’s decision could have led to thousands more lawsuits against companies nationwide, further complicating federally mandated improvements to contaminated land.

The Anaconda smelter operated between 1884 and 1980 near the small community of Opportunity, Montana, providing much of the world’s copper supply. The area is filled with creeks and streams that cross forests and farmland. It was designated as a Superfund site in 1983 to reduce arsenic contamination in residential yards, pastures and ground water.

The landowners sued in 2008 in state court to restore their properties to pre-smelter conditions. Atlantic Richfield said such state law claims were barred by the EPA’s actions under the Superfund law.

The Montana Supreme Court ruled against Atlantic Richfield in 2017.

President Donald Trump’s administration and industry lobby groups backed Atlantic Richfield, which has spent $450 million on EPA-ordered soil and ground water restoration at the site.

Monday’s ruling included a sharp exchange between Roberts and Gorsuch. Roberts sought to allay landowner concerns because the law does not apply to minor actions such as planting a garden, installing a lawn sprinkler or digging a sandbox.

That is fine, Gorsuch replied, “provided, of course, they don’t scoop out too much arsenic in the process.”

Gorsuch said the court should have allowed restoration efforts under state law and compared requiring EPA approval to “paternalistic central planning.” Roberts said it was instead the “spirit of cooperative federalism.”