The Federal Circuit on Nov. 9, 2018 held that assignor estoppel does not apply to IPRs: Arista Networks, Inc. v. Cisco Sys., Inc., No 17-1725, slip. Op. at 17-23 (Fed. Cir. Nov. 9, 2018.)

The Court held:

“We conclude that Section 311(a) [of the Patent Act], 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.” Id at 23.

This affirmed the PTAB’s practice of holding that assignor estoppel does not apply in IPRs, as set forth in the 2013 decision in Athena Automation v. Husky Injection, which was designated precedential in 2017.

Assignor estoppel is a doctrine that is still applied in district courts and the U.S. International Trade Commission. In fact, in a related ITC investigation, the ITC held that assignor estoppel applied. Assignor Estoppel is based on the concept that one cannot sell a patent, then later turn around and say that patent is invalid. The Court noted that:

“The doctrine often arises in factual scenarios similar to the facts of this case, where an employee invents something during his or her tenure with a company, assigns the rights to that invention to his or her employer, then leaves the company to join or found a competing company.” Id at 17.

The Court went on to hold:

“Section 311(a) states, in relevant part: “(a) In General.— Subject to the provisions of this chapter, 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. . . .” § 311(a) (emphasis added).

Arista contends 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.14 We agree.” Id at 21.