Public Policy Role of PTAB Clashes with Assignor Estoppel Equities
The doctrine of assignor estoppel prevents prior owners/inventors of a patent from later challenging the patent’s validity. Assignor estoppel’s premise is that the assignor “should not be permitted to sell something and later assert that what was sold is worthless, all to the detriment of the assignee.” Diamond Scientific Co. v. Ambico, Inc., 848 F.2d 1220, 1224 (Fed. Cir. 1988).
While exceptions to assignor estoppel have existed since its inception, the Federal Circuit has found that the AIA can be leveraged to circumvent the doctrine—that is, while a prior owner of a patent may not challenge the patent’s validity at district court, it may challenge the validity at the PTAB.
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