Will “Assignor Estoppel” Derail Monsanto’s Petition for Inter Partes Review?

Bernadette McGann | January 25, 2013

Pioneer has filed a Preliminary Response opposing Monsanto’s Petition for inter partes review of U.S. Patent No. 5,518,989, arguing that the Petition is merely to avoid the consequences of the doctrine of assignor estoppel.

Two of the three inventors of the ‘989 patent assigned their rights to Pioneer, and then left Pioneer to work at Monsanto.  Pioneer argues that Monsanto was able to infringe the ‘989 patent because of the knowledge and assistance of these inventors/workers.

In support of its position, Pioneer cites the CAFC’s decisions in Checkpoint and Intel.  “The doctrine of assignor estoppel prevents a party that assigns a patent to another from later challenging the validity of the assigned patent.” Checkpoint Sys., Inc. v. All-Tag Sec. S.A., 412 F.3d 1331, 1336 (Fed. Cir. 2005). The doctrine encompasses challenges by the assignor himself (typically the inventor), as well as challenges by the assignor’s privies. See, Intel Corp. v. U.S. Int’l Trade Comm’n, 946 F.2d 821, 839 (Fed. Cir. 1991).  Pioneer holds that Monsanto, the inventors’ employer, are the assignors’ privy, and thus, barred from challenging the validity of the ‘989 patent.

If the Board denies Monsanto’s petition, Pioneer might establish that Monsanto is barred from challenging the validity of the ‘989 patent.  However, if the Board grants Monsanto’s petition, Pioneer will still have another chance during the inter partes review trial to establish that Monsanto lacks the right to challenge the validity of the ‘989 patent.

Pioneer merely presented its allegation, without any evidentiary support, that Monsanto is barred by the doctrine of estoppel.  While there may be a presumption, it is unclear at this time if that is sufficient to deny the petition.

Assignor estoppel is just one of several arguments Pioneer has presented in its opposition to Monsanto’s petition for inter partes review.


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