Challenging a patent after transfer
Minerva Surgical v. Hologic
In brief
The Court kept assignor estoppel but narrowed it, wiped out the Federal Circuit’s judgment (vacated), and sent the case back (remanded) for another look.
- Where it stands
- Decided
Decided 5-4 · June 29, 2021 · Opinion by Justice Kagan
- What it’s about
- This case asked whether an inventor who assigned patent rights, and a company founded by that inventor, could later defend against an infringement suit by arguing that the patent was invalid.
- Who it affects
- The rule can block an invalidity defense only when the challenge conflicts with an explicit or implied representation made during the transfer. The Federal Circuit must apply that limit, so the dispute’s final outcome remains unresolved.
Summary: written with AI from the case record.
What it's about
The Court kept the doctrine of assignor estoppel but limited it, holding that it bars an invalidity defense only when the challenge contradicts representations the assignor made when transferring the patent.
The decision preserved a longstanding fairness rule in patent transfers while narrowing when it can block a later challenge to a patent’s validity.
Question presented
The question is 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.
What the Court decided
Holding
Assignor estoppel is well grounded in centuries-old fairness principles, and the Federal Circuit was right to uphold it. But assignor estoppel applies only when the assignor’s claim of invalidity contradicts explicit or implicit representations he made in assigning the patent. 957 F. 3d 1256, vacated and remanded.
- Result
- Vacated
The vote
From the opinions
“The Patent Act of 1952 sets forth a comprehensive scheme for the creation and protection of patent rights.”
What's next
The Federal Circuit will reconsider the case under the narrower rule. It must decide whether the invalidity argument conflicts with an explicit or implied representation made when the patent was transferred; the final infringement result remains unresolved.
Documents
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More questions
- What did the Supreme Court decide in Minerva Surgical v. Hologic?
- The Court kept assignor estoppel but limited it to invalidity challenges that conflict with explicit or implied representations made when the patent was transferred.
- Is a patent assignor still allowed to challenge validity?
- Under this rule, yes—when the invalidity challenge does not contradict an explicit or implied representation made during the patent transfer.
- What happened to the Federal Circuit’s judgment?
- It wiped out the judgment (vacated) and sent the case back (remanded) for the Federal Circuit to apply the narrower rule.
- What happens next in Minerva Surgical?
- The Federal Circuit will reconsider the case under that limit, so the parties’ final infringement outcome remains unresolved.
Sources
Primary materials plus reporting. Best-effort analysis: this explainer relies on a mix of primary materials and trusted secondary sources. Official filings and opinions remain authoritative.