Federal Circuit says Assignor Estoppel Has “No Place” in IPR Proceedings

The Federal Circuit recently found that assignor estoppel has “no place in IPR proceedings,” affirming a holding of the Patent Trials and Appeal Board (“Board”) that assignor estoppel did not bar Arista Networks (“Arista”) from attempting to invalidate a patent belonging to Cisco Systems (“Cisco”).  Arista’s founder, Dr. David Cheriton, was the inventor on the patent Arista wanted to invalidate and had previously assigned the patent to Cisco while employed by Cisco. See Arista Networks, Inc. v. Cisco Sys., Nos. 2017-1525, 2017-1577, 2018  (Fed. Cir. Nov. 9, 2018) (Before Prost, Schall, and Chen, J.) (Opinion for the court, Prost, J.).

The patent at issue—US Patent No. 7,340,597 (“the ‘597 patent”)—relates to securing network devices from external attacks by detecting and logging configuration changes in the network devices. The ‘597 patent was invented by Dr. Cheriton while he was employed by Cisco. Dr. Cheriton assigned the ‘597 patent to Cisco, but later left Cisco and founded Arista.

Arista petitioned for an inter partes review (“IPR”) of the ‘597 patent. After instituting an IPR, the Board upheld some challenged claims as patentable, but invalidated others. In reaching its decision, the Board declined to apply the doctrine of assignor estoppel to Arista, which Cisco believed should have prevented Arista from challenging the validity of the ‘597 patent. Assignor estoppel prevents a party who assigns a patent to another from later challenging the validity of the assigned patent. Arista and Cisco both appealed aspects of the Board’s decision.


On appeal, Arista argued that the Board erred in its construction of the term “broadcast,” which further caused the Board to improperly reject Arista’s obviousness arguments with respect to various claims. Cisco argued on appeal that the Board’s refusal to apply assignor estoppel to Arista was in error. The Federal Circuit affirmed Cisco’s cross-appeal but reversed and remanded with respect to Arista.

With respect to the term “broadcast,” the Board declined to adopt either party’s proposed definition, and instead defined “broadcast” based on the “ordinary and customary meaning to one of skill in the art.” However, the Court found that the Board ignored how “broadcast” was used by the patentee in the specification, and therefore reached a construction that excluded the embodiment of “broadcast” that was actually disclosed in the specification. The Federal Circuit then construed the term based on the specification and remanded for the Board to consider the patentability of the claims Arista raised on appeal based on the Court’s new construction.

The Federal Circuit addressed Cisco’s arguments regarding assignor estoppel. The Court first evaluated whether the issue was reviewable. Applying Cuozzo Speed Technologies v. Lee, 136 S. Ct. 2131 (2016) and Wi-Fi One, LLC v. Broadcom Corp., 878 F.3d 1364 (Fed. Cir. 2018), the court explained that the precedential cases “strongly point[] toward unreviewability being limited to the Director’s determinations closely related to the preliminary patentability determination or the exercise of discretion not to institute.” Since the issue of assignor estoppel is “unrelated to the Director’s preliminary patentability assessment or the Director’s discretion not to initiate an IPR,” the Court could review the issue.

Accordingly, the Court then considered whether assignor estoppel should apply in IPR proceedings. Cisco argued that assignor estoppel is a well-established common-law doctrine that should be presumed to apply unless a statute says otherwise. The Court then turned to 35 U.S.C. § 311(a), a statutory code provision addressing who may institute an IPR. The Court found that Section 311(a) “govern[ed] the question of whether Congress intended assignor estoppel to apply in the IPR context.” Section 311(a) states that “a person who is not the owner of a patent may file with the Office a petition to institute an inter partes review of the patent . . . .”

Arista argued that “§ 311(a) unambiguously leaves no room for assignor estoppel in the IPR context, given that the statute allows any person ‘who is not the owner of a patent’ to file an IPR.” The Court agreed and found that the plain statutory language unambiguously demonstrated that an assignor, who is no longer the owner of a patent, may file an IPR petition with respect to that patent. The Court concluded by stating:

In sum, we conclude that § 311(a), by allowing “a person who is not the owner of a patent” to file an IPR, unambiguously dictates that assignor estoppel has no place in IPR proceedings.

Take Away

35 U.S.C. § 311(a) allows “a person who is not the owner of a patent” to file an IPR, and therefore unambiguously dictates that assignor estoppel has no place in IPR proceedings.


Image Source: Gene Quinn.

The Author

Joseph Robinson

Joseph Robinson has over 20 years of experience in all aspects of intellectual property law. He focuses his practice in the pharmaceutical, life sciences, biotechnology, and medical device fields. His practice encompasses litigation, including Hatch-Waxman litigation; licensing; counseling; due diligence; and patent and trademark prosecution. He has served as litigation counsel in a variety of patent and trademark disputes in many different jurisdictions, and has also served as appellate counsel before the Court of Appeals for the Federal Circuit. Joe also focuses on complex inter partes matters before the U.S Patent and Trademark Office, inventorship disputes, reexaminations and reissues. His experience includes numerous interferences, a particular advantage in new U.S. Patent and Trademark Office post-grant proceedings. He also counsels on patent–related U.S. Food and Drug Administration issues, including citizen petitions, Orange Book listing, and trademark issues. For more information and to contact Joe please visit his profile page at the Troutman Sanders website.

Joseph Robinson

Robert Schaffer is an intellectual property partner at Troutman Sanders. Bob applies more than 30 years of experience to IP counseling and litigation. His work includes patent procurement, strategic planning and transactional advice, due diligence investigations, district court patent cases, and Federal Circuit appeals. He regularly handles complex and high-profile domestic and international patent portfolios, intellectual property agreements and licensing, IP evaluations for collaborations, mergers, and acquisitions. In disputed court cases Bob’s work includes representing and counseling client in ANDA litigations, complex patent infringement cases and appeals, and multidistrict and international cases. In disputed Patent Office matters his work includes representing and counseling clients in interferences, reexaminations, reissues, post-grant proceedings, and in European Oppositions. For more information and to contact Bob please visit his profile page at the Troutman Sanders website.

Joseph Robinson

Dustin Weeks is a Partner in the intellectual property practice group at Troutman Sanders. His practice spans all areas of intellectual property law, including patent prosecution, patent litigation (including Hatch-Waxman litigation), and client counseling. He represents clients ranging from start-ups and solo inventors to Fortune 500 companies. Dustin works closely with his clients to learn their business objectives so that he can tailor strategies to procure, protect, and enforce their intellectual property. Dustin specializes in post-grant proceedings (e.g. Inter Partes Reviews) before the Patent Trial and Appeal Board (PTAB) where he has extensive experience representing both patent owners and petitioners across a wide range of technologies, including wireless networking, pharmaceuticals, MEMs devices, medical devices, and electro-mechanical consumer devices. Dustin's broad experience in patent prosecution, counseling, and patent litigation uniquely positions him to navigate the blended practice of post-grant proceedings.

For more information or to contact Dustin, please visit his Firm Profile Page.

Warning & Disclaimer: The pages, articles and comments on IPWatchdog.com do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author as of the time of publication and should not be attributed to the author’s employer, clients or the sponsors of IPWatchdog.com. Read more.

Discuss this

There are currently 2 Comments comments.

  1. Joachim Martillo November 16, 2018 12:27 pm

    Because IANAL, I have to ask how Arista Networks, Inc., which is a legal person separate from Dr. Cheriton, could possibly be estopped from challenging the ‘597 patent. The assignor is Dr. Cheriton, who is a natural person. While Dr. Cheriton was founder, he may at this point just work for salary and have only negligible or no interest in Arista Networks.

  2. Anon November 16, 2018 2:46 pm

    One word, Joachim: “privy.”

    The doctrine has long “pierced” any corporate veil.