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February 11, 2013


Semiconductor Energy Laboratory (SEL) owns 6,900,463, which claims a certain semiconductor. Yujiro Nagata is the second-named of two inventors. "During prosecution in 1991, Nagata assigned his rights to applications and patents related to the '463 patent to SEL's founder Dr. Shunpei Yamazaki, and subsequently signed a substitute Declaration and Assignment of those applications and patents. From 2002 to 2003, Nagata assisted SEL in a patent infringement suit against another party and was paid for his cooperation and services relating to that litigation."

Semiconductor Energy Laboratory v. Yujiro Nagata (CAFC 2012-1245) precedential; Judges Lourie (author), Bryson and Wallach

In 2009, SEL brought suit for infringement of a number of patents, including the '463 patent, against Samsung, Inc. and others. SEL contacted Nagata for further assistance, assuming that he would cooperate as he had in the earlier case, but learned in stead that Nagata had agreed to assist Samsung in the litigation as a fact witness. During the Wisconsin proceedings, Nagata gave testimony repudiating his signature on the 1991 Declarations and Assignments. Samsung then claimed that the patents at issue, including the '463 patent, were unenforceable due to inequitable conduct, alleging that the documents were forged. The Wisconsin dispute eventually was settled, but SEL maintained that because Nagata's testimony impugned the enforceability of the '463 patent, SEL settled for less money than it would have otherwise.

So SEL went after Nagata in federal court. But Nagata got the matter dismissed with prejudice for lack of subject matter jurisdiction. SEL appealed.

The only claim asserted by SEL that purports to arise under federal law, which SEL labeled "Declaratory Judgment - Violation of Federal Patent Law," was premised on the doctrine of assignor estoppel. As we explained in Diamond Scientific Co. v. Ambico, Inc., 848 F.2d 1220, 1224 (Fed. Cir. 1988), assignor estoppel is an equitable doctrine that prohibits an assignor of a patent or patent application, or one in privity with him, from attacking the validity of that patent when he is sued for infringement by the assignee. See also Checkpoint Sys., Inc. v. All-Tag Sec. S.A., 412 F.3d 1331, 1336 (Fed. Cir. 2005) ("The doctrine of assignor estoppel prevents a party that assigns a patent to another from later challenging the validity of the assigned patent."). Assignor estoppel is thus a defense to certain claims of patent infringement.
Despite SEL's contentions, assignor estoppel is a form of estoppel, and with rare exception, estoppel is a shield; it is an affirmative defense, not a claim for relief on its own.
Accordingly, we conclude that the district court did not err in ruling that SEL's complaint did not invoke federal subject matter jurisdiction on the ground that SEL stated no claim arising under federal law.


Posted by Patent Hawk at February 11, 2013 1:32 PM | Case Law