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.
