The Supreme Court of the United States recently held in the case of Minerva Surgical, Incorporated v. Hologic, Incorporated that the doctrine of assignor estoppel (a rule that prevents people who assign their patents to a company from then challenging the validity of their patent) is alive and well, but subject to certain important exceptions.

The Validity of a Patent

In the Minerva case, the Supreme Court required the lower court to explain whether the inventor’s promise not to challenge the validity of a first patent at the time of the assignment could be held against the inventor when challenging a later patent with claims that were broader than the ones involved in the patent assigned.

The decision saw the Supreme Court apply a “non-contradiction” rule to assignor estoppel issues, which requires one to determine whether the inventor truly gave up the ability to challenge the validity of the patent in question in the assignment document. This rule will be the one to follow for all future assignor estoppel cases.

Implications for Inventors and Businesses

The Minerva decision has important implications for inventors and businesses alike. Some key take-aways are as follows:

1. Generic assignment language may create an estoppel as to a validity challenge to a claim or claims of the patent assigned, but may not cover claims of pending applications that differ in scope and claims of patents issuing from such pending applications.

   1. What role does claim construction play in the scope of any purported validity representation or estoppel?

   2. What impact does a broadening reissue or narrowing reexamination/reissue have on the scope of estoppel?

   3. Must a new assignment be submitted for continuation-in-part patent applications whose claims encompass subject matter that was not present in the applications previously assigned?

2. To the extent the Minerva decision ties a particular validity representation to claim language, assignments should seek to cover all permutations of claims to any subject matter disclosed in the subject application and/or patent.

3. Additional representations in an assignment may be required to help the assignee estop validity challenges to claims issuing from pending patent applications that are assigned. For example, assignors may try to utilize separate no-challenge clauses in their assignments, such as imposition of fines, payment of legal fees for defending against the challenge, and/or forfeiture or refund of royalties paid to the assignor.