Inventors Can Challenge their Own Patents – But Only at the PTAB

by Dennis Crouch The traditional rule of assignor estoppel prevents prior owners of a patent from later challenging the validity of the patent.  The doctrine stems from old property law cases and is based upon the idea is that the assignor “should not be permitted to sell something and later to assert that what was sold is worthless, all to the detriment of the assignee.” Diamond Scientific Co. v. Ambico, Inc., 848 F.2d 1220 (Fed. Cir. 1988); see Westinghouse Elec. & Mfg. Co. v. Formica Ins. Co., 266 U.S. 342 (1924). Of course, most ‘assignors’ are inventor-employees who assign away rights well before even conceiving of their inventions.  In his 2016 article, Mark Lemley argued that: [T]he doctrine is out of touch with the realities of both modern inventing and modern patent law, and that it interferes with both the invalidation of bad patents and the goal of employee mobility. Mark A. Lemley, Rethinking Assignor Estoppel, 54…

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