In a landmark first ruling on genetically modified crops, the US Supreme Court overturned Monday a four-year ban on alfalfa seeds engineered by biotech giant Monsanto to resist weed killer.
A California district judge voided in 2007 the Department of Agriculture's authorization of the seeds, finding that a proper environmental review had not been conducted. The decision was upheld on appeal in 2009.
But justices voted 7-1 Monday to reverse the ruling, saying the injunction overstepped the mark and prevented the agency from carrying out a "partial deregulation" of the crop, known as Roundup Resistant Alfalfa (RRA).
"We agree that the district court's injunction against planting went too far," Justice Samuel Alito wrote. "In sum, the District Court abused its discretion."
Opponents of RRA claim it could cross pollinate with conventional alfalfa seeds and other neighboring crops, promoting "super-weeds" with a tolerance to the Roundup herbicide.
"Until APHIS (the DoA's Animal and Plant Health Inspection Service) seeks to effect a partial deregulation, any judicial review of such a decision is premature," the Supreme Court said.
"The district court barred the agency from pursuing any deregulation, no matter how limited the geographic area in which planting of RRA would be allowed."
Justices ordered APHIS to carry out the long-awaited environmental impact study and referred the case back to the lower courts.
Their decision that no new claims should be filed until the study is complete opens the way for the government to allow Monsanto to resume the limited sale and planting of genetically modified alfalfa seeds.
"Until such time as the agency decides whether and how to exercise its regulatory authority, however, the courts have no cause to intervene," the ruling said.
Plaintiffs, who are organic farmers supported by organizations such as the Center for Biological Diversity, worry that genetically modified seeds will contaminate their crops.
Monsanto took the fight all the way to the highest court in the land, arguing that the federal court did not have authority to block the alfalfa seed sales. Alfalfa is the fourth most popular crop grown in the United States.
In a hearing in April, justices had appeared skeptical of the ban and questioned whether the environmental impact could have been properly assessed before the completion of the environmental impact study.
Judge Antonin Scalia minimized potential risks saying, "This is not the contamination of the New York city water supply. This isn't the end of the world. It really isn't."
The ninth Supreme Court justice, Stephen Breyer, had to recuse himself from the case because the judge who gave the initial ruling against Monsanto in California is his brother, Charles Breyer.
Explore further: Researchers devise new method to identify disease markers