The Supreme Court blocked thousands of state lawsuits against leading pesticide maker Monsanto over the ingredients in the popular weed killer Roundup, in a decision Thursday that potentially sends the tussle to Congress.

The 7-2 opinion held federal law governing pesticide labels overrides state law claims about a label failing to warn about the alleged cancer dangers of the pesticide.

In the majority opinion, Justice Brett M. Kavanaugh wrote that the Federal Insecticide, Fungicide, and Rodenticide Act, first passed in 1947, gives the Environmental Protection Agency full control over the content of pesticide labels.

Because the EPA approved a Roundup label that did not include a cancer warning, Kavanaugh wrote, Monsanto could not be sued for failing to include a cancer warning.

“In sum, federal law requires Monsanto to sell Roundup with the label that EPA approved at the initial registration and that EPA has subsequently re-approved on multiple occasions — that is, the label without a cancer warning,” Kavanaugh wrote.

The decision reversed a Missouri state court win in favor of the original challenger, John Durnell, who successfully sued Monsanto and parent company Bayer for more than $1 million. The ruling also effectively nixes thousands of state law claims against the pesticide manufacturer, as the majority wrote that Congress intended to have uniformity in labeling for those products.

Justice Clarence Thomas wrote separately in support of the overall decision but said that the underlying law may have exceeded Congress’ power to regulate commerce between states.

Justice Ketanji Brown Jackson, in a dissent joined by Justice Neil M. Gorsuch, argued that the majority ignored that Congress intended to require pesticide makers label all relevant dangers of a product, not solely the label approved by the EPA.

Jackson wrote that a provision preventing “misbranding” in the statute, mentioned separately from the EPA process, showed that “even though the EPA approved Roundup’s label, that label could still lack a necessary warning.”

She pointed out that in the past the EPA has found that its own prior approved label for Roundup didn’t meet the law’s standards and imposed fines on Monsanto for mislabeling its product by not adequately warning about a leak risk.

The Supreme Court decision likely tees up future legislative wrangling on Capitol Hill. Disputes over the lawsuit shield have complicated the passage of the current farm bill. The latest House-passed version of the bill included an amendment that stripped language requiring national “uniformity” in pesticide labeling and prohibiting state or local labelling requirements.

Rep. Anna Paulina Luna, R-Fla., the original sponsor of the amendment, warned the Senate in May not to reinstate those provisions, saying on social media that “If this comes back with those protections included, we have the votes to kill it.”

Sen. John Boozman, R-Ark., unveiled a Senate version of the bill earlier this week which did not include pesticide labeling provisions.

The case is Monsanto Co. v. Durnell.