Many farmers have ended up face-to-face with biotech giant Monsanto in court, but so far none of them have ever won. In fact, no farmer has challenged Monsanto in court without getting either 1) hammered financially like this farmer or 2) laughed out of court like these ones. But the company’s winning streak could soon come to an end.

Recently, the Supreme Court agreed to hear an appeal of a federal court ruling that Monsanto won against an Indiana soybean farmer. And while that’s no guarantee they’ll side with the farmer, I’ve often heard it said that the Supreme Court doesn’t take cases to pat the ruling judge on the back.

This particular case is a patent dispute. In fact, much of the blame (or credit) for Monsanto’s success in court lies with the U.S. Patent Office, which takes the view that things like individual product features, business techniques, website functions, and DNA are all patentable.

Of course, patent rights are just part of it. Every time Monsanto sells seeds to farmers, the company requires that they sign an incredibly strict terms-of-use agreement—in essence, a contract between Monsanto and the farmer that dictates exactly how the farmer may use the seeds. One of the agreement’s most notable clauses is the restriction against seed saving from one harvest to the next, even though Monsanto’s seeds grow “true-to-seed”; i.e., its herbicide-resistant “Roundup Ready” seeds will create corn plants whose seeds are also herbicide resistant.

Interestingly, this is not true for many conventional “hybrid” seeds, which are bred so that the next-generation seeds often result in less-desirable versions of the plant—thus causing the farmer to have to buy new seeds every year. So Monsanto has achieved through law what it could not through nature.

And while several farmers have been successfully sued for violations of this agreement, the company has also sued farmers who never signed its agreement but instead had Roundup Ready plants appear in their fields through windblown pollination (a.k.a. “contamination”). These farmers, knowingly or not, had violated Monsanto’s patent—and the courts have repeatedly upheld that conclusion.

But there is one tiny crack in Monsanto’s legal fortress. The company allows farmers to sell saved seeds from harvests of Roundup Ready crops to local grain elevators, which is where commodity crop farmers sell their harvests as well. The grain elevators mix the seeds up with other seeds from brand-name hybrids and resell them as generic seed packs, called “commodity seeds” in the trade, which are often used for late-season “second crop” planting.

Soybean farmer Vernan Bowman of Indiana saw the implications of this crack in the fortress and decided to try and drive his tractor through it.

For years, Bowman would grow a first crop of Monsanto seed, which he would purchase legally, and then would buy some commodity seed from his local grain elevator for his second crop. While aware he could not save seeds from the first crop he grew, Bowman would later plant the commodity seeds, spray the plants with Roundup, and was then able to identify which were resistant to the herbicide when they didn’t die. Bowman saved those seeds and saved money, since he had bought the commodity seeds for his second crop at a steep discount without paying Monsanto or signing its licensing agreement.

As the TechDirt blog reported at the time, Bowman was so convinced he hadn’t broken any law that he told Monsanto representatives what he’d done.