The U.S. Supreme Court on Monday backed Monsanto Co.’s efforts to control the use of its genetically modified seeds, ruling that companies have broad power to enforce patents on self-replicating technologies.

The justices unanimously upheld an $84,456 award Monsanto won in a lawsuit against an Indiana farmer who sought to circumvent the company’s patents on herbicide-resistant soybean seeds.

Rather than buying seeds from a Monsanto-authorized dealer, the farmer used harvested soybeans containing the technology to plant his crops.

Justice Elena Kagan says a farmer who buys patented seeds must have the patent holder’s permission. More than 90 percent of American soybean farms use Monsanto’s “Roundup Ready” seeds, which first came on the market in 1996.

Monsanto has a policy to protect its investment in seed development that prohibits farmers from saving or reusing the seeds once the crop is grown. Farmers must buy new seeds every year.

The case had been closely watched by researchers and businesses holding patents on DNA molecules, nanotechnologies and other self-replicating technologies. But Kagan said the court’s holding only “addresses the situation before us.”

Farmer Vernon Hugh Bowman bought the expensive, patented seeds for his main crop of soybeans, but decided to look for something cheaper for a risky, late-season soybean planting.

He went to a grain elevator that held soybeans it typically sells for feed, milling and other uses, but not as seed.

Bowman reasoned that most of those soybeans also would be resistant to weed killers, as they initially came from herbicide-resistant seeds too. He was right, and he repeated the practice over eight years. In 2007, Monsanto sued and won an $84,456 judgment.

Bowman said he should not be liable, in part, because soybeans naturally sprout when planted.

Kagan said the court did not buy that argument. “We think the blame-the-bean defense tough to credit,” she said.

The case is Bowman v. Monsanto Co., 11-796.