Federal Circuit Judge Kara Stoll.

A judge for the U.S. Court of Appeals for the Federal Circuit says the court needs to get its house in order when it comes to patent law's doctrine of assignor estoppel.

The long-controversial doctrine holds that inventors generally can't sell their patents to a third party, then turn around and attack the validity of those same patents. The U.S. Court of Appeals for the Federal Circuit carved out an exception to the rule two years ago for administrative challenges to validity made under the America Invents Act.

Federal Circuit Judge Kara Stoll on Tuesday reluctantly affirmed a district court judgment for Hologic Inc. while calling on the court for a rethink. "Given the odd circumstance created in this case, I suggest that it is time for this court to consider en banc the doctrine of assignor estoppel as it applies both in the district court and in the Patent Office," Stoll wrote in "additional views" that accompanied her opinion in Hologic v. Minerva Surgical.

The assignor in this case is Csaba Truckai, co-founder in the 1990s of a company called NovaCept Inc. and a named inventor on two NovaCept patents for endometrial ablation, a surgical process used to reduce menstrual bleeding. NovaCept sold the company and its patents to Cytyc Corp. for $325 million 2004. Cytyc in turn was acquired by Hologic.

Truckai went on to found Minerva and serve as its CEO. Hologic sued Minerva shortly after it obtained approval from the Food and Drug Administration for a competing ablation system, asserting two of the NovaCept patents. A jury awarded $4.8 million after U.S. District Judge Joseph Bataillon ruled that Minerva was estopped from challenging the validity of the patents in court.

But Minerva did succeed in invalidating one of the patents before the Patent Trial and Appeal Board, and the second patent has expired. That eliminated the possibility of ongoing royalties and an injunction blocking sales of the Minerva system, Bataillon ruled following the trial.

Hologic, represented by Arnold & Porter Kaye Scholer, argued to the Federal Circuit that the AIA could not have "abrogated the assignor estoppel doctrine in a district court infringement proceeding."

But Stoll wrote that her hands were tied by the Federal Circuit's 2018 ruling Arista Networks v. Cisco Systems. That decision held that the plain language of the AIA allows any person "who is not the owner of a patent" to bring a validity challenge at the PTO. That includes former named inventors, the court ruled in that case.

"We are mindful of the seeming unfairness to Hologic in this situation," Stoll wrote on Wednesday. "We nevertheless conclude that the district court did not abuse its discretion in denying Hologic its requested injunctive and monetary relief following a finding of patent infringement."

The good news for Hologic is that the court upheld the $4.8 million damage award on the basis of the remaining valid patent.

And the court could take up Stoll's request to rethink Arista. "We should seek to clarify this odd and seemingly illogical regime in which an assignor cannot present any invalidity defenses in district court but can present a limited set of invalidity grounds in an [AIA] proceeding," Stoll wrote.

Arnold & Porter partner Matthew Wolf argued the appeal for Hologic. Sidley Austin partner Robert Hochman argued for Minerva.