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Assignor estoppel remains unavailable as an inter partes review (IPR) defense

Overview

The Board's recent Final Written Decision in Arista Networks, Inc. v. Cisco Systems, Inc., Case IPR2016-00303, confirms that assignor estoppel remains unavailable to patent owners.

Assignor estoppel is an equitable remedy that prohibits a patent assignor, or one in privity with an assignor, from later challenging the validity of an assigned patent.