Mark A. Lemley

An issue that has bugged Lemley was resolved with a mostly positive outcome at the U.S. Supreme Court. The problem was that inventors were blocked from challenging the validity of their own patents by a doctrine known as assignor estoppel, a rule based on the idea that it would be unfair to allow an inventor to benefit from obtaining a patent and later about-face and attack the patent when that became advantageous.

“This is a doctrine that has always fascinated me because of the dramatic implications of saying you can’t defend yourself in a patent suit,” Lemley said.

The rule interferes substantially with employee mobility, Lemley contended. If an inventor starts a company, or even goes to work for an existing company in the same field, they will be “estopped” from defending a patent suit by their old employer.

In 2016, Lemley issued a call for “Rethinking Assignor Estoppel” in a law review article. Next, he affirmatively — but unsuccessfully — pushed the U.S. Court of Appeals for the Federal Circuit to correct the doctrine and watched for an exemplary case headed for the Supreme Court. Last year, he filed an amicus brief when the question did get before the justices.

And in 2021 the high court voted 5-4 that the doctrine applies only when the assignor’s claim of invalidity contradicts explicit or implicit statements the assignor made in assigning the patent. The outcome vacated a holding by the Federal Circuit and sent the case back for further litigation. Minerva Surgical Inc. v. Hologic Inc., 20-449 (S. Ct., op. filed June 29, 2021).

Writing for the majority, Associate Justice Elena Kagan twice cited Lemley’s article and held that assignor estoppel should apply only when the underlying principle of fair dealing comes into play.

“What creates the unfairness is contradiction,” she wrote, and noted Lemley’s example of an employee who assigns to his employer patent rights in any future invention he develops. The assignment contains no validity claim. “How could it?” Kagan asked. “The invention itself has not come into being.”

In the case under review, Minerva Surgical Inc.’s founder, the inventor of a surgical procedure, assigned the patent rights arising from an application that had not yet matured into an issued patent.

The patent ended up with rival Hologic Inc., which assertedly broadened the patent claims. Minerva claimed those changes left it free to challenge the patent’s validity. The justices sent the matter back to lower courts to decide the broadness issue.

“I think it’s a good outcome,” Lemley said. “The court didn’t abolish the doctrine entirely, but restricted it to circumstances where the patentee really was trying to sell their patent while concealing its problems. That’s a very small number of cases.”

- John Roemer