Assignor Estoppel

  • Assignor Estoppel Bars Patent’s Assignor Or Privity From Challenging Patent Validity: Equitable remedy barring assignor of patent, or one in privity with assignor, from challenging validity of patent if sued for infringement. Mag Aerospace (Fed. Cir. 03/23/16) (aff’g Summ. J. that defendant estopped because it hired a named inventor on asserted patent to help develop the accused system, despite that employee’s negligible financial interest in the defendant); Mentor Graphics (Fed. Cir. 03/16/17) (aff’g application of assignor estoppel; Fed. Cir. already rejected argument that Lear (U.S. 06/16/1969) abolished assignor estoppel), rehearing denied (Fed. Cir. 09/01/17) (Moore, J., concurring op. (2 judges) (Lear does not overrule Westinghouse; “The question of privity and the extent to which assignor estoppel ought to prohibit a future employer of the inventor/assignor from challenging the validity of the patent is an interesting one not raised by the parties on appeal in this case”)), CVSG (U.S. 04/23/2018); see generally Shamrock Tech. (Fed. Cir. 05/04/90) (discussing equitable factors for privity determination, and applying assignor estoppel to inequitable conduct); IGT (Fed. Cir. 05/12/16) (non-precedential) (expressly not deciding whether applies to PTAB proceedings); Arista (Fed. Cir. 11/09/18) (assignor estoppel does not apply to IPR proceedings: “§ 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,” and the statute does not provide that all equitable defenses apply (unlike ITC proceedings)).

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