The closely watched decision was a clear victory for agribusiness giants and their biotechnological innovations, which have increased crop yields. But it was a setback for the many disgruntled farmers who have complained about the high cost of these miracle seeds.
By a 9-0 vote, the justices decided the patent for a specialized seed outlives the first planting. Otherwise, these patents, and the huge investment that went into developing the modified seeds, "would be largely worthless," Justice Elena Kagan explained in court.
In 1980, the high court helped trigger the biotech revolution in agriculture and medicine when it ruled for the first time that a living organism could be patented. That decision upheld a patent for a bacteria that could break down crude oil.
In the decades since, farming has been transformed by genetically modified seeds that produce bountiful crops that can ward off disease as well as weed killers. A handful of giant multinational firms, led by Monsanto, dominate the market for seeds for commercial crops.
Industry leaders were stunned last year when the Supreme Court agreed to hear an Indiana farmer's challenge to this system of patents and profits.
Vernon Hugh Bowman, 75, a farmer from southern Indiana, conceded that he liked Monsanto's Roundup Ready seeds. They produced strong soybean plants that can tolerate weed killers.
Each year, Bowman bought the costly Monsanto seeds for his first crop of the season. But in an effort to save money, he turned to what the court described as a "less orthodox" approach for his second crop of the season.
Rather than pay again for more Monsanto seeds, he bought soybeans from a local grain elevator. This mixture, which came from nearby fields, contained soybeans that had been grown from Roundup Ready seeds. Bowman used this method over eight years and spoke proudly of it in the community.
But when Monsanto learned of Bowman's scheme, the company sued him for patent infringement. Monsanto insisted Bowman was using its patented seeds without paying for them.
A trial judge agreed and awarded the company $84,456 in damages. A special federal appeals court upheld that decision, and the U.S. solicitor general advised the court to reject Bowman's appeal.
But the justices voted to hear Bowman's claim based on the doctrine of "patent exhaustion." The farmer and his lawyer argued that once Monsanto had sold seeds to Bowman and other farmers, it had earned its just profit from the sale. At this point, they said, the company's patent rights were exhausted.
If the high court had accepted that argument, its decision could have upset industries that depend on years of profit from their patented inventions, potentially including vaccine makers and developers of computer software.
Putting those fears to rest Monday, the justices decided the doctrine of "patent exhaustion" cannot be applied generally to products such as seeds, which reproduce themselves.
"Bowman planted Monsanto's patented seeds solely to make and market replicas of them, thus depriving the company of the reward patent law provides from the sale of each article," Kagan wrote in Bowman v. Monsanto. "Patent exhaustion provides no haven for that conduct."
Monsanto's general counsel, David Snively, said the decision "provides assurance to all investors throughout the public and private sectors that they can and should continue to invest in innovation."
The Center for Food Safety in San Francisco, a critic of the so-called seed giants, said the decision was a "setback for the nation's farmers" and that it "improperly attributes seeds' reproduction to farmers, rather than nature."
In her opinion, Kagan referred to this as the "blame-the-bean defense" and one she had no problem rejecting.
"It was Bowman, not the bean, who controlled the reproduction (unto the eighth generation) of Monsanto's patented invention," she said.