Supreme Court Will Review Doctrine of Assignor Estoppel

On Friday, the U.S. Supreme Court granted a petition for certiorari filed by Minerva Surgical, Inc. asking the Court to clarify questions around the doctrine of assignor estoppel. Specifically, the petition presents the question: “Whether a defendant in a patent infringement action who assigned the patent, or is in privity with an assignor of the patent, may have a defense of invalidity heard on the merits.”

Hologic, Inc. and Cytyc Surgical Products, respondents in the case, also filed a cross-petition for certiorari in November. That petition asks the Court to address “whether an assignor of a patent may circumvent the doctrine of assignor estoppel by challenging the validity of the assigned patent in administrative proceedings before the Patent Office, and then using the Patent Office’s finding of invalidity to collaterally estop the assignee from relying on the patent in infringement litigation in district court.”

Reluctant Federal Circuit

In April of last year, the U.S. Court of Appeals for the Federal Circuit (CAFC), in Hologic, Inc. v. Minerva Surgical, Inc., affirmed—with some hesitation—a decision of the  U.S. District Court for the District of Delaware holding that assignor estoppel did not bar an assignor from relying on a CAFC decision affirming a Patent Trial and Appeal Board (PTAB) decision invalidating asserted claims in an inter partes review (IPR) proceeding. With respect to a second patent-in-suit, the CAFC affirmed the district court’s summary judgment that assignor estoppel barred the assignor from asserting invalidity of the assigned second patent in district court. Read more about the underlying case here.

Judge Stoll wrote separately in that decision to note that the case highlighted an “odd situation where an assignor can circumvent the doctrine of assignor estoppel by attacking the validity of a patent claim in the Patent Office, but cannot do the same in district court.” Stoll noted that the Court’s precedent in Arista Networks, Inc. v. Cisco Sys., Inc., 908 F.3d 792,803– 04 (Fed. Cir. 2018) held that the doctrine of assignor estoppel does not apply in the context of an inter partes review (IPR), while precedent such as Mentor Graphics Corp. v. EVE-USA, Inc., 851 F.3d 1275, 1280–83 (Fed. Cir. 2017) continues to preclude assignors from challenging the validity of their assigned patents in district court. Thus, Stoll suggested that “it is time for this court to consider en banc the doctrine of assignor estoppel as it applies both in district court and in the Patent Office” in order 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 IPR proceeding.” However, the Court denied en banc rehearing and the parties petitioned the Supreme Court.

Minerva: Assignor Estoppel Must be Nixed

In its petition, Minerva argues that the judicially created doctrine of assignor estoppel should be eliminated altogether. “Assignor estoppel undermines, rather than serves, patent law values,” says the petition. “Nonetheless, the Federal Circuit not only has continued to apply this textually groundless doctrine, it has expanded it at every opportunity.” Minerva notes that, despite its self-made rule on assignor estoppel, the Federal Circuit held in Arista that assignor estoppel does not apply in IPRs, leaving the court “at odds with itself.” A similar doctrine, “licensee estoppel”, was also rejected by the High Court in Lear, Inc. v. Adkins, 395 U.S. 653 (1969).

If the Court declines to reject the doctrine completely, it should still accept the case to “define its very limited contours,” says the petition. In the present case, Minerva says, “the Federal Circuit expanded assignor estoppel to bar petitioner Minerva from raising invalidity defenses that arose only because the ultimate assignee of the patent rights, respondent Hologic, had broadened the scope of the patent beyond anything the inventor had claimed.” Rather than asserting that what the inventor assigned was worthless–the stated rationale for the doctrine in the first place–Minerva’s defense is that, “more than ten years after the inventor assigned the patent…. Hologic took the old assigned patent specification, drafted and prosecuted a new patent claim broader than what the inventor had claimed or assigned, and wielded that claim against Minerva,” says the petition.

Hologic: It’s Intuitive

In their separate cross-petition, which has not been granted, Hologic/Cytyc argue that “[b]arring this Court’s intervention, the decision below will eviscerate the assignor estoppel doctrine and encourage duplicative litigation, forum shopping, and other forms of gamesmanship.” And in their opposition to Minerva’s petition, Hologic and Cytyc argue that assignor estoppel is “a simple, intuitive rule” that “precludes inventors who have assigned (i.e., sold) the rights to an invention from later challenging the validity of the rights they sold.” Granting Minerva’s request to abrogate the doctrine would represent a “revolutionary step” and eliminate “a baseline protection that this Court first endorsed almost a century ago and against which Congress has legislated.”

Amici Back Minerva

Amicus briefs have been filed by Intellectual Property Professors (authored by Mark Lemley) and Engine Advocacy thus far, supporting Minerva’s position. Lemley’s brief contends that “[t]he doctrine has expanded far beyond the metes and bounds of this Court’s increasingly narrow precedent, including to cases lacking any bad faith during negotiations and to cases where not only the inventor herself but also her privies are precluded from challenging an invalid patent.”

Engine Advocacy argues that the doctrine’s expansive application shields “low-quality patents (e.g., patents that are vague, overbroad, claim what is known in prior art, or otherwise cover inventions that ought not be considered patentable) from scrutiny.” The brief continues:

The doctrine of assignor estoppel, by design, limits the courses of action one may take when seeking to challenge low-quality patents. Such patents are often the bane of a startup’s existence, to the extent that they frequently stand in the way of innovation. For that reason alone, if it has any proper place in the law, assignor estoppel should be very narrowly-tailored.

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