Plain-English summary
Court narrows assignor estoppel: former patent owners can sometimes challenge validity
In Minerva Surgical v. Hologic (2021), the Supreme Court limited the reach of the assignor-estoppel doctrine. The Court held that assignor estoppel applies only when an assignor’s invalidity argument contradicts representations made when assigning the patent.
Why this matters
This decision narrows a longtime judicially created limit on who can challenge a patent’s validity. It makes it easier in some situations for a former owner of a patent to raise invalidity defenses, which can affect patent litigation strategies, licensing deals, and transactions that involve assigning patent rights.
Who may feel it
- Patent holders and assignees (companies that acquire patent rights)
- Former patent owners (assignors) who might later challenge patents
- Patent licensees and businesses involved in patent transfers
- Patent litigants and patent attorneys
Key questions
- Does the judge-made doctrine of assignor estoppel bar a patent’s former owner from asserting the patent is invalid in all cases?
- If assignor estoppel applies, what standard determines when it bars an assignor’s invalidity defense?