J. Derek Mason

The doctrine of assignor estoppel has been around for over a century and most often applied in the U.S. International Trade Commission (ITC) and U.S. district courts to prevent a first party assigning a patent to a second party from then challenging the validity of the patent they had just assigned. In a November 9, 2018 decision, the U.S. Court of Appeals for the Federal Circuit ruled that the doctrine of assignor estoppel does not apply in the inter partes review (IPR) context (see Arista Networks, Inc. v. Cisco Systems, Inc., (Fed. Cir. 2018). This raises intriguing possibilities regarding how companies might be able to protect themselves. One possibility might be to revise their employment agreements for signing by new employees.