By Lawrence Hurley 

WASHINGTON, Feb 21 (Reuters) - During oral argument in a major patent case this week, it became clear that the U.S. Supreme Court was unlikely to resolve a key legal question raised in the dispute.

The court is weighing whether 75-year-old farmer Vernon Bowman circumvented the law by planting a soybean crop containing Monsanto Co patented technology that he had not purchased from an authorized dealer.

Monsanto said such a use of its Roundup Ready technology, which protects crops from herbicides, was unlawful. Bowman said because the grain he used as seed was "second generation" and not the first-generation sold by seed dealers, it was not covered by the patent.

Oral arguments were heard on Tuesday. Patent law experts said the court may have taken the case in large part to resolve what Justice Sonia Sotomayor described during the argument as "lingering confusion" over the type of conditions patent holders can impose on sales of their products.

"I think that the conditional sales issues were the original highlight for the court," said Dennis Crouch, a patent law expert at the University of Missouri School of Law.

The conditional sales doctrine, as it is called, has been embraced by the U.S. Court of Appeals for the Federal Circuit in several cases. Under that doctrine, the court has found that patent rights are not exhausted after any authorized sale.

That stance has been a target for criticism from various quarters, including the Obama administration, which argues that it is inconsistent with a 2008 Supreme Court ruling, Quanta v. LG Electronics, which said patent rights are exhausted after an authorized sale. Patent law experts think the Supreme Court is looking for the right case that would allow it to address the issue.

Bowman's attorneys said the Federal Circuit applied the doctrine in the Monsanto case, although the company and the Obama administration say the court did not rely on it in reaching its conclusion. The Obama administration joined in Tuesday's arguments in support of the Federal Circuit ruling that found Bowman had infringed Monsanto patents despite its opposition to the conditional sale doctrine.

During Tuesday's argument, the justices went in a different direction. Instead of focusing on Monsanto's effort to control the use of subsequent generations of seeds, they appeared to be leaning toward a finding that Bowman violated the patent when he "made" new copies of the protected product. He did this when he grew crops using seeds he had purchased and then used the seeds generated from that crop to plant a new crop.

"You know there are certain things that the law prohibits," Justice Stephen Breyer told Bowman's lawyer, Mark Walters. "What it prohibits here is making a copy of the patented invention. And that is what he did."

Sotomayor specifically asked Monsanto's attorney, Seth Waxman, whether the court needed to - or should - address the conditional sales issue.

"I think that an appropriate case will come up where it will be important for you to determine that," Waxman responded.

Experts expect the court now to rule in favor of Monsanto on the basis that Bowman infringed the patent due to an authorized "making" of a copy.

When the court initially accepted the case, the justices might have thought the so-called "conditional sale" issue was key. But upon reading the briefs they may have realized that the case could be decided in a more "straightforward way," said Adam Mossoff, a law professor at George Mason University School of Law.

Once the case reached the oral argument stage, "they thought it was almost a no-brainer," he added.

Several experts familiar with the case said they expected the conditional sales issue to be raised in a concurring opinion in what could be a 9-0 ruling in favor of Monsanto.

Crouch predicted that the concurring opinion will say that "the Federal Circuit's conditional sale doctrine is bad law and that restrictions on the use of personal property do not normally bind subsequent purchasers who are not privy to that restriction agreement."

The case is Bowman v. Monsanto, U.S. Supreme Court, No. 11-796.

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